Practice Test


1) A drop of radius one micron carries a charge of 4e. If the density of oil is 2g/cc, the electric field held required to balance its is :


2) The distance between two plates of a cathode ray oscilloscope is 1 cm and potential difference between them is 1200 V. If an electron of energy 2000eV enters at right angles to the field, what will be the deflection if the plates are 1.5 cm long ?


3) In a Thomson's set up for e/m, the same high tension d.c. supply provides potential to anode for acceleration and also the potential to anode for acceleration and also the positive voltage to the deflecting plate in the region of crossed fields. If the supply voltage is doubled, by what factor the magnetic field be increased to keep the electron beam undeflected ?


4) In Millikan's oil drop method, an oil drop having a charge 'ne' is held stationary by applying a potential difference of 400 V between two parallel plates. If the size of the drop is doubled without changing the charge, the potential difference required to keep its stationary is :


5) Doubly ionised helium atoms and hydrogen ions are accelerated through the same potential. The ratio of the final velocities of helium and of the hydrogen ions is :


6) The ratio of specific charge e/m of an electron to that of a Hydrogen ion is :


7) In a mass spectrograph, an ion A of mass number 24 and charge +e and an ion B of mass number 22 and charge +2e both enter the same magnetic field with the same velocity. The radius of circular path of A is 24cm, then the radius of circular path of B is :


8) The mass of proton is 1837 times that of an electron. An electron and a proton are injected into a uniform electric field at right angles to the direction of the field with the same kinetic energy. Then :


9) An electron and a proton are injected into a uniform electric field at right angles to the direction of the field with equal momentum. Then :


10) An electron and a proton are injected into a uniform magnetic field at right angles to the direction of the field with the same momentum Then :


11) An electron beam passes through a magnetic field of B tesla and electric of E volt/meter acting simultaneously and in mutually perpendicular direction. If the electron beam remains undeviated, the speed of electron beam must be :


12) Cathode rays moving with same velocity v describe an approximate circular path of radius r meter in an electric field of strength x volt/ meter. If he speed of the cathode rays is doubled to 2v, the value of electric field needed so that the rays describe the same approximate circular path (volt/meter) is :


13) Radiations of energies twice and five times the work function of metal are incident turn by turn. The ratio of max. velocities of photoelectrons in two cases will be :


14) The maximum kinetic energy of the photo-electrons released when it is stopped by 2v of negative potential is :


15) The ratio of wavelength of 10 KeV photon with that of 10 KeV electron is :


16) Photoelectric work function of a metal is 4eV. What is the maximum wavelength to which the metal is photosensitive ?


17) Bragg's equation will have no solution if :


18) An electron and a proton are having same total energy, then de-Broglie wavelength is :


19) The energy required to remove an electron in a hydrogen atom from n = 10 state is :


20) Consider the spectral line resulting from the transition n = 2 to n = 1 in the atoms and ions given below, the shortest wavelength is produce by :


21) When a photon of energy 7eV is made incident on a metal then the emitted electron is stopped by a stopping potential of -5.5 V. The work function of metal will be:


22) The ratio of wavelength of a photon and that of an electron of same energy will be :


23) A photon of wavelength 0.1 A is emitted by a helium atom. The recoil energy of the atom as a consequence of emission of photon will be :


24) The uncertainty in the measurement of position of an electron of energy 1 Ke V is 1 A. The percentage uncertainty in the measurement of its momentum will be :


25) In an X-rays tube, if the electrons are accelerated through 140 KV then anode current obtained is 30mA. If the whole energy of electrons is converted into heat then the rate of production of heat at anode will be :


26) When ultraviolet radiation is incident upon a surface, no photo-electrons are emitted. If a second beam causes photo-electrons to be ejected, it may consist of :


27) If 10% of the energy supplied to an incandescent light bulb is radiated as visible light, then the number of photons emitted by a 60W bulb per second will be :


28) If the distance of 100 W lamp is increased from a photo cell, the saturation current in the photo cell varies with distance d as :


29) A radio transmitter operates at a frequency of 800 kHz and a power of 10 kW. The number of photons emitted per second is :


30) Which one of the following graphs represents correctly the variation of photoelectric current (i) with intensity (l) of incident radiations :


31) For three different metals A,B,C photo-emission is observed one by one and maximum kinetic energy (K) versus frequency (v) of incident light graphs are plotted.Which fig. represents the curves correctly ?


32) A photo cell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 2 m away, the electrons emitted by the photo cathode :


33) Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively successively illuminate a metal of work function 0.5 eV. The ratio of maximum speeds of the emitted electrons will be :


34) The maximum kinetic energy of photo-electrons emitted from a surface when photons of energy 6 eV tall on it is 4 eV. The stopping potential in volts is :


35) Photons of energy 6 eV fall on a photometal of work function 4 eV. The minimum kinetic energy of emitted photoelectrons is :


36) A small photocell is placed at a distance of 4m from a photosensitive surface. When light falls on the surface the current is 5mA. If the distance of cell is decrease to 1m, the current will become :


37) The velocity of the most energetic electrons emitted from a metal surface is doubled when the frequency v of incident radiation is doubled. The work frequency of the metal is :


38) The energy of incident photon is 12.375 eV while the energy of scattered photon is 9.375 eV. Then the kinetic energy of recoil electron is :


39) In Compton effect incident X-ray photon has energy 12.4 keV. If the energy of scattered photon is 6.4 keV, the kinetic energy of recoiled electron is :


40) The ratio of momenta of an electron and an alpha particle which are accelerated from rest through a potential difference of 100 volts is :


41) The mean free path of electron in a discharge tube is 15 cm. The length of tube is 10cm. The length of the Crooke's dark space is :


42) In Millikan's oil drop experiment an oil drop of radius r and charge Q is held in equilibrium between the plates of a charged parallel plate capacitor, when the potential difference is V. To keep a drop of radius 2r, having a charge 2Q in equilibrium between the plates, the potential difference V required is :


43) A charged oil drop is held stationary in an electric field. The space containing the drop is exposed to a radioactive source and drop moves with different terminal velocities V, 2V, 3V, 4V..... etc. It suggests :


44) In an electron microscope if the potential is increased from 20kV to 80 kV, the resolving power R of the microscope will become :


45) A photon recoils back after striking an electron at rest. What is the change in wavelength of the photon ?


46) The voltage across the electrodes of a cathode ray gun is 500 volts. Calculate the momentum of the electrons.


47) An electron beam passes through a parallel plate condenser. The electric intensity between plates is 20 V/cm, the distance between plates is 5cm and the length of the path traversed by beam as 10cm. Calculate the deflection angle of the beam.


48) Electrons which have been accelerated by a potential difference of 1000 V enter co-terminus electric and magnetic fields of strengths 20 V/cm and 1G respectively as in the Thomson's experiment. Estimate speed of electrons if they move undeviated through the system.


49) The deflecting plates in a Thomson's set up are 5.0 cm long and 1.5 cm apart. The plates are maintained at a potential difference of 240 V. Electrons accelerated to an energy of 2.0 keV enter from one edge of the plates midway in a direction parallel to the plates. What is the deflection at the other edge of the plates ?


50) In a positive ray apparatus singly ionised and doubly ionised particles form identical parabolae when the magnetic fields are respectively 5 and 7.5 tesla. Compare the masses of the particles, assuming the electric field to be same.


51) A hydrogen atom at rest in the second excited state emits photon when it jumps to the ground state. Calculate the de-Broglie wave-length of the hydrogen atom. Energy of ground state = - 13.6 eV.


52) A photoelectric cell is illuminated by a small bright source of light placed at 1m. If the same source of light is placed 2 m away, the electrons emitted by the cathode :


53) In a discharge tube at 0.1 mm of Hg there is a formation of :


54) Light of frequency 1.5 times the threshold frequency is incident on a photo-sensitive material. If the frequency is halved and the intensity is doubled, the photoelectric current is doubled, the photoelectric current becomes :


55) According to Bohr's theory, the electron in orbits have definite energy values, then according to uncertainty principle, the life time of a n excited state will be :


56) The energy of a photon corresponding to the visible light of maximum wavelength is approximately :


57) A particle of mass 1g is located in a box of size 2 cm. The uncertainty in the momentum of the electron will be :


58) In a mass spectrograph, an ion A of mass number 24 and charge +e and an ion B of mass number 22 and charge +2e both enter the same magnetic field with the same velocity. The radius of circular path of A is 24 cm, then the radius of circular path of B is :


59) When X-rays are scattered by electrons their wavelength increases. Their phenomenon is called :


60) In a photoelectric cell, the current stops when the collecting, plate is one volt negative with respect to emitting metal. The maximum kinetic energy of the photoelectrons is :


61) The number of complete de-Broglie wavelengths associated with the electron in nth orbit of hydrogen atom is :


62) Einstein's work on the photoelectric effect provided support for the equation :


63) Who indirectly determined the mass of the electron by measuring the change of the electron ?


64) An oil drop carrying a charge q has a mass m kg. It is falling freely in air with terminal speed v. The electric field required to make the drop move upwards with the same speed is :


65) A particle with a specific charge S is fired with a speed v towards a wall at a distance d, perpendicular to the wall. What minimum magnetic field must exist in this region for particle not to hit the wall ?


66) Kinetic energy of emitted electron depends upon :


67) Electron with energy 80 keV are incident on the tungsten target of an X-ray tube. K shell electrons of tungsten have -72.5 keV energy. X-rays emitted by the tube contain only :


68) An ionised gas contains both positive and negative ions. If its is subjected simultaneously to an electric field along the + x direction and a magnetic field along the + z direction, then :


69) Particle nature and wave nature of elector-magnetic wave and electrons be shown by :


70) Intensity of X-ray depends upon number of :


71) The energy of X-rays is 2keV, then frequency is :


72) The de-Broglie wavelength of electron of energy 600 eV is :


73) Gases begin to conduct electricity at low pressure because :


74) The electric field required to keep a water drop of mass m just to remain suspended when charged with one electron is :


75) The most important characteristic of electrons in the production of X-rays is :


76) Which one among the following shows particle nature of light ?


77) A photocell is illuminated by a source of light placed at a distance d. It distance is decreased to d/2, then no. of electron emitted by it :


78) The work function of oxide coated tungsten emitter will be :


79) If work function of metal is 3 eV then threshold wavelength will be :


80) When ultraviolet rays incident on metal plate then photoelectric effect does not occur, it occurs by incident of :


81) Which of the following is not the property of cathode rays :


82) An electron having charge e and mass m is moving in an electric field E. Its acceleration will be:


83) The potential difference applied to an X-ray tube is 5 kV and the current through is 3.2 mA. Then the number of electrons striking the target per second is :


84) J.J-Thomson's cathode-ray tube experiment demonstrated that :


85) Characteristic X-rays are produced due to :


86) Photoelectric effect shows :


87) For a given kinetic energy which of the following has the smallest de-Broglie wavelength ?


88) The phenomenon inverse to photoelectric effect is :


89) The rest mass of a photon is :


90) If the wavelength of the incident light changes from 400 nm to 30 nm, the shopping potential for photoelectrons emitted from a surface becomes approximately


91) A photon of energy 4 eV is incident on a metal surface whose work function is 2eV. The minimum reverse potential to be applied for stopping the emission of electrons is :


92) The magnitude of saturation photoelectric current depends upon :


93) Monochromatic light incident on a metal surface emits electrons with kinetic energies from zero to 2.6 eV. What is the least energy of the incident photon if the tightly bound electron needs 4.2 eV to remove ?


94) Which of the following have highest specific charge ?


95) The wavelength of matter wave is independent of :


96) A photo cell employs photoelectric effect to convert :


97) In a discharge tube ionisation of enclosed gas is produce due to collisions between :


98) Flash light equipped with a new set of batteries produce bright white light. As the batteries wear out :


99) Determine the value of n for which the de- Broglie wavelength corresponding to nth orbit is equal to wavelength of nth line of Lyman series. Given Z = 11.


100) Stopping potential required to reduce the photoelectric current to zero :


101) The photoelectric threshold frequency of a metal is v. When light of frequency 4v is incident on the metal, the max, kinetic energy of the emitted photo-electrons is :


102) When light of wavelength 300 nm falls on a photoelectric emitter,photo-electrons are liberated. For another emitter, light of wavelength 600nm is sufficient for liberating photo-electrons. The ratio of the work function of two emitters is :


103) Which of the following figure represents the variation of particle momentum and associated de-Broglie wavelength ?


104) The energy of a photon of light of wavelength 450 nm is :


105) The slope of frequency of incident light and stopping potential for a given surface will be :


106) Which of the following statement is correct ?


107) An electron and photon have same de-Broglie wavelength. Then kinetic energy of electron is


108) A radio-transmitter radiates power of 1kW at wavelength 198.6 m. How many photons does it emit per sec ?


109) A parallel plate B is charged to 100 V while plate A is earthen, with separation of 1cm. A third metal plate C is introduced at a distance of 1/3 from A. An electron starts from plate A. What is minimum potential applied to C, So that electron will not reach B ?
______________________ B
______________________ C
______________________ A
+


110) Two parallel beam of electrons moving in the same direction, produce a mutual force :


111) Wave is associated with matter, when :


112) The light rays are incident on a metal surface. The light photons have an energy 1.8 eV and the work function of the metal is 1.2 eV. What amount of stopping potential is to be applied to stop the electrons from emitting ?


113) Of which the specific charge is highest ?


114) Cathode rays are a stream of :


115) If the energy of a photon is increased by a factor of 4, its momentum :


116) The phenomenon inverse of photoelectric effect is :


117) A beam of electrons passes through undetected through mutually perpendicular electric and magnetic fields. If the electric is switched off and the same magnetic field is maintained, the electrons move :


118) The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of the incident radiation for which the stopping potential is 5 V lies in the :


119) In the phenomenon of electric discharge through gases at low pressure, the coloured glow in the tube appears as a result of :


120) Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per sec on the average at a target irradiated by this beam is :


121) Two positive ions, each carrying a charge q, are separated by a distance d. If F is the force of repulsion between the ions, the number of electrons missing from each ion will be (e being the charge on an electron )


122) A beam of cathode rays is subjected to crossed Electric (E) and Magnetic fields (B). The fields are adjusted such that the beam is not deflected the specific charge of the cathode rays is given by :


123) Which one of the following bonds produces a solid that reflects light in visible region and whose electrical conductivity decreases with temperature and has high melting point ?


124) Photoelectric emission occurs only when the incident light has more than a certain minimum :


125) In the Davission and Germer experiment, the velocity of electrons emitted from the electrons gun can be increased by :


126) Electron used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de-Broglie wavelength associated with the electrons would :


127) In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is :


128) Silver has a work function of 4.7 eV. When ultraviolet light of wavelength 100 nm is incident upon it, a potential of 7.7 V is required to stop the photoelectrons from reaching the collector plate. How much potential will be required to stop photoelectrons when light of wavelength 200 nm is incident on silver ?


129) In a photoelectric experiment, the stopping potential is V, when the frequency of incident radiation is f and V' when the frequency of incident radiation is 2f. The value of (V' - V) is :


130) A proton, a deutron and an alpha particle are accelerated by same potential difference. Their velocity will be in the ratio:


131) The mass of a proton is 1840 times that of an electron. An electron and proton of same initial kinetic energy enter normally in a uniform electric field.


132) The specific charge of an electron is :


133) Which of the following is (are) not deflected by electric and magnetic fields ?


134) The energy of a photon of X-rays of wavelength 1A.U is :


135) The de-Broglie wavelength of an electron having kinetic energy 500 eV is :


136) The electron is nearly 200 times lighter than a proton. An electron and a proton are moving so that their matter wave have a wavelength of 1 A.U. The ratio of their kinetic energies is :


137) The photoelectric effect supports quantum theory of light because :


138) Lights of two different frequency whose photons have energies 2 eV and 2.5 eV respectively successively illuminate a metal whose work function is 0.5 eV. The ratio of the maximum speeds of the emitted electrons will be :


139) A bulb of 10 W is at distance of 10 km from a man. How many photons are entering into the eye per second if the diameter of the eye is 2mm ?


140) If the kinetic energy of the moving particles is E, then the de-Broglie wavelength is :


141) The work function of a metal surface is 4.2 eV. The maximum wavelength which can eject electrons from this metal surface is :


142) Neglecting variation of mass with energy the wavelength associated with an electron, having a kinetic energy E is proportional to :


143) X-rays absorption will be maximum for sheets of :


144) In a photoelectric experiment, photons of energy 5 eV are incident on a metal surface. The liberated photoelectrons are first stopped an electrode at a potential of 3.5 V. The work function of the metal surface is :


145) The hardness of X-rays can be increased :


146) Mosley's law related to :


147) Velocity of an electron whose mass is ten times its rest mass is :


148) Ratio of the specific charge of a proton to that of an electron is :


149) For a spectral line of wavelength 400 A.U the energy in eV of the photon associated with it, is :


150) X-rays of wavelength 1 A.U. when scattered in a Compton scattering in transverse direction, will have an increase in wavelength of :


151) The shortest wavelength of X-rays emitted from an X-ray tube depends on :


152) According to Bohr's theory the relation between main quantum number 'n' and radius of the orbit is :


153) What is the energy of an emitted photon when the hydrogen atom changes from an energy state of n = 5 to n = 4 ?


154) A hydrogen atom emits blue wavelength when the transition takes place n = 4 to n = 2. In which colour it would emit when the transition is form n = 5 to n = 2 ?


155) For ionising an excited hydrogen atom the energy 'E' required in eV will be :


156) The energy gap between successive energy levies in a hydrogen atom, with increasing order of 'n' :


157) A spectral line resulting the transitions n = 2 to n = 1 in the atoms are given below. Which of these produces shortest wavelength ?


158) The energy required to excite a hydrogen atom from n = 1 to n = 2 is 10.2 eV. What is wavelength emitted by atom when it returns to ground state ?


159) The speed v of the electron in an orbit of radius r is :


160) The first and the last member of the Lyman series are :


161) The ionisation potential of hydrogen atom is 13.6 eV. The energy required to remove the electron from second orbit is :


162) If the ionization energy for the hydrogen atom is 13.6 electron- volts, the energy required to excite it from the ground state to the next higher state is nearly :


163) The ratio of K.E and total energy of the electron in hydrogen atom as per Bohr's model is :


164) The ionisation potential of hydrogen is 13.6 eV. If the atom is excited by a monochromatic beam of 12.1 eV, the spectral lines emitted will be :`


165) In an atom two electrons move round the nucleus in circular orbits of radii R and 4R. The ratio of the time taken by them to complete one revolution is :


166) An electron revolves round the nucleus of charge Ze. In order to excite the electron from the state n = 2 to n = 3, the energy required is 47.2 eV. The value of Z is :


167) Which of the following is true ?


168) In which region of e.m. spectrum does the Lyman series of hydrogen lie ?


169) The angular momentum of electron in nth orbit is given by :


170) The energy required to remove an electron in a hydrogen atoms from n = 10 state is :


171) The velocity of an electron in ground state is :


172) Adsorption coefficient of X-rays for given wavelength is larger for


173) The ionisation potential for H-atom is 14V. The K-level for atom with Z = 80 should therefore, be closest to :


174) The ratio of the energies of hydrogen atom in its first and second excited states is :


175) Doubly ionised helium atom and hydrogen ion are accelerated from rest through the same potential helium difference. The ratio of the final velocities of helium and hydrogen ion is :


176) The stopping potential for the photoelectrons emitted from a metal of work function 1.7 eV is 10.4 V. Identify the energy levels in H-atom which emit this wavelength :


177) The wavelength of the first line of the Lyman series for Hydrogen is same as that of second line of Balmer series for some hydrogen like atom X. what is the Z-value of X ?


178) The ratio between K.E and the total energy of election of hydrogen atom accordingly to Bohr's model is :


179) The speed of an electrons in the orbit of hydrogen atom in the ground state is :


180) The ratio of magnetic dipole moment of an electron of charge e and mass in Bohr's orbit in hydrogen to its angular momentum is :


181) The ratio of the radius of the orbit of the electron orbiting the hydrogen nucleus to that of an electron orbiting a deutrium nucleus is :


182) The wavelength of the first line of the Lyman series for Hydrogen is same as that of second line of Balmer series for some hydrogen like atom X.Find the ionisation potential for X.


183) Rydberg's constant R is equal to :


184) The shortest wavelength emitted in Lymen series is :


185) The difference in the angular momentum of the electron in the two successive orbits of hydrogen atom is :


186) In an electronic transition, atom cannot emit :


187) The kinetic energy and potential energy of the orbital electron in the hydrogen atom taking into consideration their signs as T and U, which of the following gives the total energy of electron ?


188) When a particle and anti-particle combine the result is a :


189) For a stability of nucleus the relations between N number of neutrons and Z atomic number should be as :


190) When two protons attract each other :


191) Which of the following particle is unstable ?


192) The mass defect in a nuclear fusion is 0.03 per cent. Energy liberated in one kilogram of fusion is :


193) The half-line of radon is 3.8 days. After how many days will 1/10th of a radon sample remain behind ?


194) The decay constant of a radioactive element whose half life period is 1620 years is :


195) Radioactive element has a half life of 10 days. How much element will be left after a period of 40 days if the original amount of element is 2gms ?


196) The half-life of radioactive element depends on :


197) A radioactive isotope has a half life period of 5 years. The fraction which decays in 15 years is :


198) Half-time of an element is 140 days. Out of 16g, the 15g of element will decay in :


199) Two radioactive substances 'X' and 'Y' initially contain equal number of atoms. 'X' has half-life of one hour and 'Y' has half of 2 hours. After 2 hours the ratio of the rate of disintegration of 'X' to that of y is :


200) The mass defect in a nucleus with Z = 2 and A= 4 is 0.04 a.m.u. The B.E. per nucleon is :


201) When one gm of mass is converted into energy, the energy released in kWh is :


202) During a nuclear reaction, protons are destroyed producing an energy of 3724 MeV. The number of protons destroyed is :


203) A freshly prepared radioactive source of half-life 2 hours emits of intensity which is 64 times the permissible safe level. The minimum time after which it is possible to work safely with this source is :


204) Two radioactive substances 'X' and 'Y' have half - lives of T and 2T respectively. Samples of 'X' and 'Y' contain equal number of nuclei initially. After a time 4T,the ratio of undecayed atoms of 'X' to the undecayed atoms of 'Y' is :


205) The radioactivity of an element becomes 1/64th of its original value in 60sec. The half-life period is :


206) The mass of He is 4 and that of sulphur is 32.The radius of the sulphur nucleus is large than that of helium by the factor of :


207) A certain radioactive element has half life period of 20 years. If we have a block with 10 g if the element, after how many years will there be just 2.5 g of the element left in the block ?


208) A G.M counter used for measurement of the activity records 2400 counts/ minute at a certain instant and after an hour the count drops to 300 per minute. What is the half- life of the substance ?


209) An atom can be considered as having a dense nucleus of neutrons and protons with surrounding distribution of electrons. If there are x- neutrons, y- protons and z- electrons, then what sort of relation exist between x, y and z in a small neutral atom ?


210) The half life of radioactive radon is 3.8 days. The time at the end of which 1/20th of Randon sample will remain undecayed is :


211) A sample contains 16 gms of radioactive material, the half life of which is 2 days. After 32 days, the amount of sample left is :


212) A certain element disintegrates for an interval of time equal to its mean life. The fraction of the original amount that remains undecayed is


213) What percentage of the original radioactive atom is left after 5 half lives ?


214) A radio isotope has half life of 75 years. The fraction of this material that would decay in 150 years will be :


215) At ordinary temperature when we pass light through a tube filled with hydrogen then in the absorption spectrum :


216) When the electron has a transition from the state (n + 1) to state n, then frequency v of the emitted radiation will be proportional to :


217) According to Bohr's theory of hydrogen atom, the angular momentum of electron in any orbit of hydrogen is :


218) What percentage of radioactive substance is left after 5 half life periods ?


219) An energy of 24.6 eV is required to remove one electron from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is :


220) If the speed of the electron in a hydrogen atom orbit of principal quantum number n be v. Then the curve showing variation of v with n is :


221) If the hydrogen atoms are excited to states with principal quantum number n, then the number of possible emission lines is :


222) The difference in frequencies of series limit of Lymen series and Balmer series is equal to the frequency of the first line of the :


223) A hydrogen atom in the ground state absorbs 12.09 eV of energy. The change in the orbital angular momentum of the electrons is :


224) The area of the electron orbit for the ground state of hydrogen atom is A. Then what will be area of the electron orbit corresponding to the first excited state ?


225) First excitation potential of an atom is E. What will be the ionisation potential ?


226) In a hydrogen like atom, the energy required to excite the electron from IInd to the IIIrd orbit is 47.2 eV. What is the atomic number of the atom ?


227) A gas of monoatomic hydrogen is bombarded with a stream of electrons that have been accelerated from rest through a potential difference of 12.75 volt. In the emission spectra one cannot observe the lines of :


228) When the electron jumps from a level n = 4 to n = 1 level, the momentum of the recoiled hydrogen atom will be :


229) If 10% of a radioactive material decay in 5 days, then amount of original material left after 20 days is approximately :


230) The half life period of neutron is 13 minutes approximately. The intensity of neutron beam traveling in free space with a velocity of 30 km per sec is reduced to half when it cover a distance of :


231) A radioactive element X with a half life of 2 hours decays giving a stable element Y. After a time t, the ratio of X to Y atoms is 1 : 7, then time t is :


232) The radioactive nucleus of an element X decay to a stable nucleus Y. A graph of the rate of formation of Y against time t, would be looking like


233) The counting rate observed from the radioactive source at t = 0 second was 1600 counts/sec and t = 8sec, it was 100 counts/sec. The counting rate per sec at t = 6sec will be :


234) Over what distance in free space will the intensity of a 5 eV neutron beam be reduced by a factor one half ? (T = 12.8 min)


235) When an electron jumps from the fourth orbit to the second orbit, one gets the :


236) Some amount of radioactive substance (half life = 10 days) is spread inside a room and consequently the level of radiation becomes 50 times the permissible level for normal occupancy of the room. After how many days the room will be safe for occupation ?


237) Nuclear force exists between :


238) In the sum about 4 billion kg of matter is converted to energy each second. The power output of the sun is watt is :


239) It is possible to understand nuclear fission on the basis of the :


240) Atomic hydrogen has a life period of :


241) Half-life of a substance is 20 minutes. What is the time between 33% decay and 67% decay ?


242) The approximate value of quantum number n for the circular orbit of hydrogen 0.0001 mm in diameter is


243) The isotope generally used for blood cancer is :


244) When 3d orbital is complete, the new electron will enter in :


245) An ionized gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the +x direction and a magnetic field along the +z direction, then :


246) The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true ?


247) If N denotes the concentration of a radioactive element,then the rate of change of concentration with time (t) can be written as :


248) Which one among the following shows particle nature of light ?


249) What is binding energy of hydrogen nucleus ?


250) What determines half-life of a radioactive element ?


251) Source of sun's energy is :


252) Rutherford's X-ray scattering by particle concluded that :


253) Which of the following is wrongly matched ?


254) The half-life period of a substance is 1600 years. Then the amount of substance will become .......... of its initial value in 6400 years :


255) The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then :


256) Which of the following Indian got a Nobel Prize in Physics ?


257) The wavelength of light emitted from second orbit to first orbit in a hydrogen atom is :


258) 10 g of radioactive material of half life 15 years is kept in store for 20 years. The disintegrated material is :


259) Recently some particles have been discovered travelling with more than the velocity of light, they are :


260) The half life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days :


261) The electron emitted in beta radiation originates from :


262) Which of the following has highest neutron ratio ?


263) In an atom bomb energy us released by :


264) Which of the following are suitable for the fusion process ?


265) Which one of the following is the weakest kind of bonding in solids ?


266) Heavy water is used as a modulator in nuclear reactor. The function of the modulator is :


267) A sample of an element is 10.38g. If half - life of element is 3.8 days then after 19 days how much quantity of element remains ?


268) The solar energy is mainly caused due to:


269) The volume occupied by an atom is greater than the volume of the nucleus by a factor of about :


270) The mass number of a nucleus is :


271) A sample radioactive element has a mass of 10g at an instant t = 0. The approximate mass of this element in the sample after two mean lives is :


272) In which of the following systems will the radius of the first orbit (n = 1) be minimum ?


273) For uranium nucleus, how does its mass vary with volume ?


274) A laser beam is used for carrying out surgery because it :


275) A radioactive substance decays to 1/16th of its initial activity in 40 days. The half - life of the radioactive substance expressed in days is :


276) Nuclear fusion is possible :


277) Radioactive nuclei that are injected into a patient collect at certain sites within his body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tool called :


278) The percentage of mass covered to energy during nuclear reaction is :


279) When an electron is emitted from a nucleus, then effect on its neutron - proton ratio will :


280) Which one of the following is most fissionable ?


281) The percentage of fissionable mass in uranium 235 is :


282) Which of the following has the same mass as that of electron ?


283) Shorter wavelength is of :


284) For a given value of n, the possible number of electron is :


285) The half-life time period of radium is 1600 years, its decay constant shall be :


286) The half life of radium is about 1600 years. Of 100g of radium existing now, 25g will remain unchanged after :


287) Natural uranium contains about :


288) If the ionization potential of hydrogen atom is 13.6 eV then the ionization potential of Lithium is :


289) The Bohr model of atoms :


290) The energy difference between first two levels of hydrogen atom is 10.2 eV. For another element of atomic number 10 and mass number 20, this will be :


291) For an electron in a hydrogen atom the frequency of photon for transition between levels 1 and 2 is v. The photon frequency for transition between levels 2 and 3 is close to :


292) If R is Rydberg's constant then unit of Paschen series is :


293) The energy level to which electron jumps from higher level to produce Balmer series of hydrogen atom is :


294) The percentage change in the angular momentum of the electron when the transition is from 2nd to 1st orbit of hydrogen atom is :


295) If L is the angular momentum of the electron in the second orbit of hydrogen atom, then the angular momentum in third orbit is :


296) When hydrogen atom is raised from the ground state to an excited state the potential energy increases and K.E.


297) After x half life times the fraction of amount which remains undecayed is :


298) The fraction of a sample of radium that would remain after 4800 years is (take half life of radium = 1600 years) :


299) The experimentally measured dissociation energy of Lil is :


300) The Magnetic Resonance Imaging (MRI) is based atom on the phenomenon of :


301) We wish to see inside an atom. Assuming the atom to have a diameter of 100 pm, this means that one must be able to resolve a width of say 10 pm. If an electron microscope is used, the minimum electron energy required is about :


302) After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another 140 days. The initial activity of the sample in dps is :


303) A large scale destruction that would be caused due to use of nuclear weapons is known as :


304) The nuclei of which one of the following pairs of nuclei are isotones ?


305) In any fission process, the ratio
mass of fission products / mass of parent nucleus is :


306) Fission of nuclei is possible because the binding energy per nucleon in them :


307) The total energy of an electron in the first excited state of hydrogen atom is about -3.4 eV. Its kinetic energy is :


308) The ground state energy of hydrogen atom is - 13.6 eV. What is the potential energy of the electron in this state ?


309) A radioactive material has a half-life of 10 days. What fraction of the material would remain after 30 days ?


310) If a star can convert all the He nuclei completely into oxygen nuclei, the energy released per oxygen nucleus is [Mass of He nucleus is 4.0026 a.m.u. and mass of Oxygen nucleus is 15.9994 a.m.u] :


311) The radius of Ge nuclei is measured to be twice that of 9/4 Be. The no. of nucleons in Ge are :


312) Which of the following is not a pair of isotopes ?


313) The ionisation energy of 10 times ionised sodium atom is :


314) A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by :


315) Half lives of two radioactive substances A and B are respectively 20 minute and 40 minute. Initially the sample of A and B have equal number of nuclei. After 80 minutes, the ratio of number of A and B nuclei is :


316) If half-life of a radioactive atom is 2.3 days, then its decay constant would be :


317) The binding energy per nucleon is maximum in the case of :


318) Minimum excitation of Bohr's first orbit is hydrogen atom is:


319) If the binding energy of the deutrium is 2.23 MeV. The mass defect given in a.m.u is :


320) A radio-isotope has a life of 5 years. The fraction of the atom of this material that would decay in 15 years will be :


321) Average number of neutrons emitted per fission is :


322) Critical mass of a fissionable material can be reduced by :


323) Which of the following is most unstable ?


324) Check the correctness of the following statements about Bohr model of hydrogen atom :
(i) the acceleration of the electron in n = 2 orbit is more than in n = 1 orbit.
(ii) the angular momentum of the electron in n = 2 orbit is more than in n = 1 orbit.
(iii) the K.E. of the electron in n = 2 orbit is less than in n = i orbit.


325) The binding energy of the innermost electron in tungsten is 40 keV. To produce the characteristic X- rays, using a tungsten target in an X-ray tube, the potential difference V between the cathode and the anti-cathode should be :


326) The rest energy of an electron is 0.511 MeV. The electron is accelerated from rest to a velocity 0.5 c. The change in its energy will be :


327) When an atom undergoes an alpha decay, its :


328) In hydrogen atom, the transition that emit radiation in the visible region is :
(n is the principal quantum number)


329) A radioactive isotope has a half life of T years. The time after which its activity is reduced to 6.25% of its original activity is :


330) The energy in sun is produces by :


331) Suppose I mg of a radioactive substance is taken initially. After 2 hours it is found that 0.25 mg of the substance is left behind. The mean life of the substance is :


332) Which one of the following is a natural source of gamma radiation ?


333) A radioactive material has life of the one hour. Then the fraction of the material that remains without disintegration at the end of 4 hours is :


334) What is the radius of 2nd Bohr orbit, given the radius of the first Bohr orbit is r.


335) Mosley's law relates :


336) In simple of radioactive material, what fraction of the initial number of active nuclei will remain un-distintegrated after half- life of the sample ?


337) One milligram of matter is converted into energy, the energy released will be :


338) Two nuclei have their mass numbers in the ratio of 1 : 3. The ratio of their nuclear densities would be :


339) The ground state energy of hydrogen atom is -13.6 eV. When its electron is in the first excited state, its excitation energy is :


340) The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an :


341) The ionization energy of the electron in the hydrogen atom in its ground state is 13.6 eV. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between :


342) The wavelength of the first line of laymen series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is :


343) The half life of a radioactive isotope 'Y' is 50 years. It decays to another element 'Y' which is stable. The two elements 'X' and 'Y' were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be :


344) A radioactive nucleus of mass M emits a photon of frequency v and the nucleus recoils. The recoils energy will be :


345) Which one of the following is possible nuclear reaction ?


346) Which of the following is the Einstein's photoelectric equation can be written as ?


347) In the above question how many photons per second on an average are emitted by source ?


348) What is the de Broglie wavelength associated with an electron accelerated through a potential difference of 100 volts.


349) The photoelectric cut-off voltage in a certain experiment is 1.5 V. The maximum kinetic energy of photoelectrons emitted is


350) Monochromatic light of wavelength 632.8 nm is produced by a He-Ne laser. The power emitted is 9.42 m W. How many photons per second on the average,arrive at a target irradiated by this beam ?


351) For light bean of wavelength 632.8 nm, what is the momentum of each photon in the beam ?


352) A 100 W sodium lamp radiates energy uniformly in all directions. The lamp is located at the center of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589 nm. At what rate are the electron delivered on the sphere ?


353) The work function of a certain metal is 4.2 eV . Which among the wavelengths 390 nm, 440 nm, 550 nm and 760 nm will this metal give photoelectric emission ?


354) An X-ray tube produces a continuous spectrum of radiation with its short wavelength end at 0.45 A. What is the maximum energy of a photon in the radiation.


355) According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal vs the frequency of the incident radiation gives a straight line whose slope


356) Dual nature of radiation is shown by


357) In a photoelectric cell, illuminated with a certain radiation, the minimum negative anode potential with respect to emitting metal required to stop the electron is 2 V. The maximum kinetic energy of photoelectron is


358) The photoelectrons emitted from a surface of sodium metal are such that


359) An ultraviolet light source causes the emission of photoelectrons from a zinc plate. A more intense source of the same wavelength would give
Maximum energy of electron No. of electrons / second


360) The retarding potential for having zero photoelectron current


361) Statement 1 : Electron microscope uses variable wavelengths of electrons for different resolving powers.
Statement 2 : As the accelerating voltage is increased, the wavelength of electron decreases


362) The difference in maximum kinetic energy of photoelectrons from A and from B


363) The threshold wavelength of A and B are related as :


364) What is the ratio of the wavelengths of a photon and that of an electron of the same energy ?


365) The de-Broglie wavelength of an electron is same as that of a photon. If the velocity of electron is 50% of the speed of light, then ratio of kinetic energy of photon to the kinetic energy of electron is


366) An electron and a proton enter a magnetic field perpendicularly. Both have same kinetic energy. Which of the following is true ?


367) Which of the following graphs correctly represents the variation of particle momentum with associated de - Broglie wavelength ?


368) J.J.Thomson's cathode - ray tube experiment demonstrated that


369) Photon is the name given to


370) Statement 1 : Though light of a single frequency is incident on a metal, the energies of emitted photoelectrons are different.
Statement 2 : The energy of electrons emitted from inside the metal surface is lost in collision with the other atoms in the metal


371) Statement 1 : Photoelectric effect demonstrates the particle nature of electrons.
Statement 2 : The number of photoelectrons is proportional to the frequency of light.


372) The number of photons falling per seconds on each square metre of earth's surface directly below the sun is


373) The number of photons in each cubic metre near the earth's surface is


374) The number of photons emitted by the sun per second


375) A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity, then


376) Which phenomenon best supports the theory that matter has a wave nature


377) Consider the following statements concerning electrons :
I. Electrons are universal constituents of mater.
II. J J Thomson received the very first Nobel prize in Physics for discovering the electron.
III. The mass of the electron is about 1/2000 of a neutron.
IV. According to Bohr the linear momentum of the electron is quantised in the hydrogen atom. Which of the above statements are not correct?


378) The working principle of the mass spectrograph is that for a given combination of accelerating potential and magnetic field, the ion beam (with charge q and mass M) to be collected at different positions of ion collectors will depend upon the value of


379) Electric field and magnetic field in Thomson mass spectrograph are applied


380) If the wavelength of light is 4000 Å, then the number of waves in 1 mm length will be


381) A 100 W light bulb is placed at the centre of a spherical chamber of radius 0.10m. Assume that 66% of the energy supplied to the bulb is converted into light and that the surface of chamber is perfectly absorbing. The pressure exerted by the light on the surface of the chamber is


382) Momentum of a photon is p. The corresponding wavelength is


383) Penetrating power of X-rays depends on


384) If V be the accelerating voltage, then the maximum frequency of continuous X-rays is given by


385) Solid targets of different elements are bombarded by highly energetic electron beams. The frequency (f) of the characteristic X-rays emitted from different targets varies with atomic number Z as


386) If the momentum of an electron is changed by ∆ p, then the de-Broglie wavelength associated with it changes by 0.50%. The initial momentum of the electron will be


387) If the wavelength of incident light changes from 400 nm to 300 nm, the stopping potential for photoelectrons emitted from a surface becomes approximately


388) In a photoelectric experiment for 4000 Å incident radiation, the potential difference to stop the ejection is 2V. If the incident light is changed to 3000 Å, then the potential required to stop the ejection of electrons will be


389) If a photon has velocity c and frequency v, then which of following represents its wavelength


390) What is de-Broglie wavelength of electron having energy 10 ke V?


391) An oil drop with charge q is held stationary between two plates with an external potential difference of 400 V. If the size of the drop is doubled without any change of charge, the potential difference required to keep the drop stationary will be


392) Planck’s constant has the dimensions of


393) The de-Broglie wavelength is proportional to


394) Intensity of X-rays depends upon the number of


395) The work functions of metals A and B are in the ratio 1:2. If light of frequencies f and 2f are incident on the surfaces of A and B respectively, the ratio of the maximum kinetic energies of photoelectrons emitted is (f is greater than threshold frequency of A,2f is greater than threshold of B)


396) The minimum wavelength of X-rays produced in a coolidge tube operated at potential difference of 40 kV is


397) The energy of a photon of light with wavelength 5000 Å is approximately 2.5 eV. This way the energy of an X-ray photon with wavelength 1Å would be


398) An electron is accelerated through a potential difference of V volt. The speed of electrons will be


399) The frequency of the incident light falling on a photosensitive metal plate is doubled, the kinetic energy of the emitted photoelectron is


400) For an electron in the second orbit of Bohr’s hydrogen atom, the moment of linear momentum is


401) The ratio transmitter operates on a wavelength of 1500 m at a power of 400 kW. The energy of radio photon (in joule) is


402) In an X-rays tube, the intensity of the emitted X-rays beam is increased by


403) Light of wavelength 4000 Å is incident on a metal plate whose work function is 2 eV. The maximum KE of the emitted photoelectron would be


404) Kinetic energy of emitted cathode rays is dependent on


405) In Davisson - Germer experiment maximum intensity is observed at


406) According to photon theory of light which of the following physical quantities associated with a photon do not/does not change as it collides with an electron in vacuum


407) For characteristic X-ray of some material


408) What is the de-Broglie wavelength of the α-particle accelerated through a potential difference V


409) Light of wavelength 1824 Å, incident on the surface of a metal, produces photo-electrons with maximum energy 5.3 eV. When light of wavelength 1216 Å is used, the maximum energy of photoelectrons is 8.7 eV. The work function of the metal surface is


410) The de-Broglie wavelength of a ball of mass 120 g moving at a speed of 20 m/s is


411) The potential difference applied to an X-ray tube is 5kV and the current through it is 3.2 mA. Then the number of electrons striking the target per second is


412) What should be the velocity of an electron so that its momentum becomes equal to that of a photon of wavelength 5200 Å?


413) An electron of mass m and charge q is accelerated from rest in a uniform electric field of strength E. The velocity acquired by it as it travels a distance l is


414) e/m ratio of anode rays produced in a discharge tube, depends on the


415) The continuous X-rays spectrum produced by an X-ray machine at constant voltage has


416) The de-Broglie wavelength associated with the particle of mass m moving with velocity v is


417) Work function of a metal is 2.51 eV. Its threshold frequency


418) A photon in motion has a mass


419) The mean free path of the electrons in a discharge tube is 20 cm. The length of the tube is 15 cm only. Then length of Crooke’s dark space is


420) When subjected to a transverse electric field, cathode rays move


421) An electromagnetic radiation has an energy of 13.2 keV. Then the radiation belongs to the region of


422) The resistance of a discharge tube is


423) Which one of the following statements regarding photo-emission of electrons is correct?


424) The work function for metals A,B and C are respectively 1.92 eV,2.0 eV and 5 eV. According to Einstein’s equation, the metals which will emit photo electrons for a radiation of wavelength 4100 Å is/are


425) A beam of light of wavelength λ and with illumination L falls on a clean surface of sodium. If N photoelectrons are emitted each with kinetic energy E, then


426) A electron moving with a variable linear velocity v in a variable magnetic field B will remain rotating in a circle of constant radius r only when


427) If particles are moving with same velocity, then maximum de-Bronglie wavelength will be for


428) The maximum kinetic energy of emitted electrons in a photoelectric effect does not depend upon


429) Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V. the threshold frequency of the material is


430) Which is the incorrect statement of the following


431) The threshold wavelength for photoelectric emission from a material is 4800 Å. Photoelectrons will be emitted from the material, when it is illuminated with light from a


432) Light of wavelength 4000 Å incident on a sodium surface for which the threshold wavelength of photoelectrons is 5420 Å. The work function of sodium is


433) When an inert gas is filled in place of vacuum in a photo cell, then


434) A 5 W source emits monochromatic light of wavelength 5000Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0m, the number of photoelectrons liberated will be reduced by a factor of


435) Millikan’s oil-drop experiment established that


436) The material used for making thermionic cathode must have


437) Consider the two following statements I and II, and identify the correct choice given in the answers
III. In photovoltaic cells the photoelectric current produced is not proportional to the intensity of incident light.
IV. In gas filled photoemissive cells, the velocity of photoelectrons depends on the wavelength of the incident radiation.


438) A light having wavelength 300 nm falls on a metal surface. Work function of metal is 2.54 eV. What is stopping potential?


439) An oil drop carrying a charge q has a mass m kg. It is falling freely in air with terminal speed v. The electric field required to make the drop move upwards with the same speed is


440) Which of the following event, support the quantum nature of light?


441) The de-Broglie wavelength L associated with an elementary particle of linear momentum p is best represented by the graph


442) When yellow light is incident on a surface, no electrons are emitted while green light can emit. If red light is incident on the surface, then


443) Which of the following is accompanied by the characteristic X-ray emission


444) Assuming photoemission to take place, the factor by which the maximum velocity of the emitted photoelectrons changes when the wavelength of the incident radiation is increased four times, is


445) When the light source is kept 20 cm away from a photo cell, stopping potential 0.6 V is obtained. When source is kept 40 cm away, the stopping potential will be


446) The most penetrating radiation out of the following is


447) The potential difference applied to an X-ray tube is increased. As a result, in the emitted radiation


448) The photoelectric effect represents that


449) Ultraviolet radiation of 6.2 eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy of the faster electron emitted is approximately


450) If an electron and a photon propagate in the form of waves having the same wavelength, it implies that they have the same


451) If intensity of incident light is increased in PEE then which of the following is true


452) For intensity I of a light of wavelength 5000Å the photoelectron saturation current is 0.40 μA and stopping potential is 1.36 V, the work function of metal is


453) Threshold wavelength for photoelectric emission from a metal surface is 5200Å. Photoelectrons will emitted when this surface is illuminated with monochromatic radiation from


454) In photoelectric effect, the KE of electrons emitted from the metal surface depends upon


455) A particle which has zero rest mass and non-zero energy and momentum, must travel with a speed


456) During X-ray production from coolidge tube if the current in increased, then


457) The ratio of the energy of an X-ray photon of wavelength 1 Å to that of visible light of wavelength 5000 Å is


458) The photoelectric threshold wavelength for a metal surface is 6600Å. The work function for this metal is


459) X-rays of which of the following wavelengths are hardest


460) A metal surface is illuminated by a light of given intensity and frequency to cause photoemission. If the intensity of illumination is reduced to one-fourth of its original value, then the maximum kinetic energy of the emitted photoelectrons would become


461) The minimum wavelength of photon is 5000 Å, its energy will be


462) Doubly ionised helium atom and hydrogen ions are accelerated, from rest, through the same potential difference. The ratio of final velocities of helium and hydrogen is


463) Energy of electrons can be increased by allowing them


464) Which of the following wavelength fall in X-ray region


465) The correct curve between the stopping potential (V) and intensity of incident light (I) is


466) The velocity of photon is proportional to (where v is frequency)


467) The wavelength of X-rays is


468) In a photoelectric effect experiment, the slope of the graph between the stopping potential and the incident frequency will be


469) The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately


470) Cathode rays and canal rays produced in a certain discharge tube are deflected in the same direction if


471) An electron in the hydrogen atom jumps excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 eV, then the value of n is


472) The colour of the positive column in a gas discharge tube depends on


473) If alpha, beta and gamma rays carry same momentum, which has the longest wavelength?


474) Photon of frequency v has a momentum associated with it. If c is the velocity of light, the momentum is


475) An electron initially at rest is accelerated through a potential difference of 1V. The energy acquired by electron is


476) The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately


477) A charge of magnitude3e and mass 2m is moving in an electric field E. The acceleration imparted to the charge is


478) For the production of X-rays, the target should be made of


479) In cathode ray oscillograph, the focusing of beam on the screen is achieved by


480) Order of q/m ratio of proton, α-particle and electron is


481) Cathode rays are


482) The structure of solid crystals is investigated by using


483) An electron of charge 'e' coulomb passes through a potential difference of V volts. Its energy in 'joules' will be


484) What should be the velocity of an electron so that its momentum becomes equal to that of a photon of wavelength 5200Å ?


485) The ratio of the de Broglie wavelengths of an electron of energy 10 eV to that of person of mass 66 kg travelling at a speed of 100 km/hr is of the order of


486) The continuous x-ray spectrum obtained from a Coolidge tube is of the form


487) The maximum velocity of an electron emitted by light of wavelength λ incident on the surface of a metal of work function ϕ, is
Where h= Planck’s constant, m= mass of electron and c= speed of light


488) Electrons with de-Broglie wavelength λ fall on the target in an X-ray tube. The cut-off wavelength of the emitted X-rays is


489) Penetrating power of X-rays can be increased by


490) The difference between kinetic energies of photoelectrons emitted from a surface by light of wavelength 2500Å and 5000Å will be


491) A metal surface of work function 1.07 eV is irradiated with light of wavelength 332 nm. The retarding potential required to stop the escape of photoelectrons is


492) In an X-ray tube electrons bombarding the target produce X-rays of minimum wavelength 1 Å. What must be the energy of bombarding electrons


493) In a discharge tube ionization of enclosed gas is produced due to collisions between


494) The filament current in the electron gun of a coolidge tube is increased while the potential difference used to accelerate the electrons is decreased. As a result, in the emitted radiation


495) Positive rays consists of


496) When light of wavelength 300 nm falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, light of wavelength 600 nm is sufficient for liberating
photoelectrons. The ratio of the work function of the two emitter is


497) The maximum wavelength of radiation that can produce photoelectric effect in certain metal is 200 nm. The maximum kinetic energy acquired by electron due to radiation of wavelength 100 nm will be


498) The retarding potential for having zero photo-electron current


499) If the threshold wavelength for sodium is 5420 Å, then the work function of sodium is


500) From the following, what charges can be present on oil drops in Millikan’s experiment
(Here e is the electronic charge)
Zero, equal to the magnitude of charge on


501) Which of the following metal thermionically emits an electron at a relatively lowest temperature among them


502) Which of the following figures represents the variation of particle momentum and associated de-Broglie wavelength?


503) The work function of a metal is 1eV. Light of wavelength 3000 Å is incident on this metal surface. The velocity of emitted photoelectrons will be


504) A photo-sensitive material would emit electrons, if excited by photons beyond a threshold. To overcome the threshold, one would increase the


505) Positive rays were discovered by


506) The frequency and intensity of a light source are doubled. Consider the following statements
I. Saturation photocurrent remains almost the same.
II. Maximum kinetic energy of the photoelectrons is doubled.


507) If an electron moves from rest from a point at which potential is 50 V to another point at which potential is 70 V, then its kinetic energy in the final state will be


508) If wavelength of photon and electron is same then ratio of total energy of electron to total energy of photon would be


509) In photoelectric effect if the intensity of light is doubled, then maximum kinetic energy of photoelectrons will become


510) Which of the following statements is not correct


511) In photoelectric effect, the electrons are ejected from metals if the incident light has a certain minimum


512) Photo cell is a device to


513) An electron microscope is used to probe the atomic arrangement to a resolution of 5 Å. What should be the electric potential to which the electrons need to be accelerated


514) In the photoelectric effect the velocity of ejected electrons depends upon the nature of the target and


515) The slope of frequency of incident light and stopping potential graph for a given surface will be


516) Ultraviolet radiations of 6.2 eV falls on an aluminium surface. KE of fastest electron emitted is (work function = 4.2 eV)


517) J. J. Thomson’s cathode ray tube experiment demonstrated that


518) A metal block is exposed to beams of X-ray of different wavelengths X-rays of which wavelength penetrate most


519) For the structural analysis of crystals, X-rays are used because


520) If we express the energy of a photon in KeV and the wavelength in angstroms, then energy of a photon can be calculated from the relation


521) Cathode rays enter a magnetic field making oblique angle with the lines of magnetic induction. What will be the nature of the path followed?


522) The threshold wavelength for photoelectric effect of a metal is 6500 Å. The work function of the metal is approximately


523) A beam of cathode rays is subjected to crossed Electric (E) and Magnetic field (B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by


524) Mosley’s law relates the frequencies of line X-rays with the following characteristics of the target element


525) Particle nature and wave nature of electromagnetic waves and electrons can be shown by


526) A photon and an electron have an equal energy E.


527) A photon of wavelength 4400 Å is passing through vacuum. The effective mass and momentum of the photon are respectively


528) An electron and photon have same wavelength. If E is the energy of photon and p is the momentum of electron, then the magnitude of E/p in SI unit is


529) A cesium photocell, with a steady potential difference of 60V across, is illuminated by a bright point source of light 50 cm away. When the same light is placed 1m away the photoelectrons emitted from the cell


530) Which of the following is not the property of the photons?


531) Stopping potential required to reduce the photoelectric current to zero


532) The time taken by a photoelectron to come out after the photon strikes is approximately


533) In a region, steady and uniform electric magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a


534) The threshold frequency for a metallic surface corresponds to an energy of 6.2 eV and the stopping potential for a radiation incident on this surface is 5V. The incident radiation lies in


535) In a photoelectric experiment, if both the intensity and frequency of the incident light are doubled, then the saturation photoelectric current


536) The mass of a proton is 1836 times that of an electron. An electron and a proton are projected into a uniform electric field in a direction perpendicular to the field with equal initial kinetic energies. Then


537) The minimum wavelength of X-ray emitted by X-rays tube is 0.4125 Å. The accelerating voltage is


538) An electron and a proton have the same de-Broglie wavelength. Then the kinetic energy of the electron is


539) A photo-cell employs photoelectric effect to convert


540) The magnitude of saturation photoelectric current depends upon


541) The photoelectric threshold frequency of a metal is v. When light of frequency 4v is incident on the metal. The maximum kinetic energy of the emitted photoelectrons is


542) For photoelectric emission, tungsten requires light of 2300 Å. If light of 1800 Å wavelength is incident then emission


543) In Millikan’s oil drop experiment a drop of charge Q and radius r is kept constant between two plates of potential difference of 800 V. Then charge on other drop of radius 2 r which is kept constant with a potential difference of 3200 V is


544) An electron and a neutron can have same (1) kinetic energy, (2) momentum, or (3) speed. Which particle has a shorter de-Broglie wavelength?


545) The specific charge for positive rays is much less than that for cathode rays. This is because


546) In producing X-rays a beam of electrons accelerated by a potential difference V is made to strike a metal target. For what value of V,X-rays will have the lowest wavelength of 0.3094 Å


547) On increasing the number of electrons striking the anode of an X-ray tube, which one of the following parameters of the resulting X-rays would increase?


548) If the frequency of light incident on metal surface is doubled, then kinetic energy of emitted electron wii become


549) The velocity, v, at which the mass of a particle is double its rest mass is


550) Photoelectric effect can be explained by


551) An electron and a proton are moving in the same direction with same kinetic energy. The ratio of the de- Broglie wavelength associated with these particles is


552) According to Einstein’s photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is


553) Vidicon works on the principle of


554) The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function of the metal is (hc =1240 eV-nm)


555) A photon collides with a stationary hydrogen atom in ground state inelastically. Energy of the colliding photon is 10.2 eV. After a time interval of the order of micro second another photon collides with same hydrogen atom inelastically with an energy of 15 eV. What will be observed by the detector?


556) The de-Broglie wavelength of an electron in the ground state of the hydrogen atom is


557) The number of photo-electrons emitted per second from a metal surface increases when


558) When wavelength of incident photon is decreased then


559) The work function of metal is 1 eV. Light of wavelength 3000 Å is incident on this metal surface. The velocity of emitted photo-electrons will be


560) The de-Broglie wavelength λ


561) A photon of wavelength 6630 Å is incident on a totally reflecting surface. The momentum delivered by the photon is equal to


562) A charged particle of mass m and charge q is released from rest in an uniform electric field E neglecting the effect of gravity,the kinetic energy of the charged particle after t second is


563) X-rays are known to be electromagnetic radiations. Therefore the X-ray photon has


564) Photoelectric effect supports quantum nature of light because
I. There is minimum frequency of light below which no photoelectrons are emitted.
II. Electric charge of photoelectrons is quantized.
III. Maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity.
IV. Even when metal surface is faintly illuminated the photoelectrons leave the surface immediately.


565) X-ray are diffracted from a crystal of lattice plane spacing 2Å. The maximum wavelength that can be diffracted is


566) Among the following four spectral regions, the photons has the highest energy in


567) Four particles have same momentum. Which has maximum kinetic energy?


568) Photons of energy of 6 eV are incident on a metal surface whose work function is 4 eV. The minimum kinetic energy of the emitted photoelectrons will be


569) A ratio transmitter operates at a frequency 880 kHz and a power of 10 kW. The number of photons emitted per second is


570) The average energy of the Planck oscillator is


571) If an electron and a photon propagate in the form of waves having the same wavelength, it implies that they have the same


572) If the energy of photon is increased by a factor of 4, then its momentum


573) An X-ray has a wavelength of 0.010 Å. Its momentum is


574) If a proton and electron have the same de Broglie wavelength, then


575) If the kinetic energy of a free electron doubles, its de-Broglie wavelength changes by the factor


576) Threshold wavelength for photoelectric effect on sodium is 5000 Å. Its work function is


577) If an electron and a proton have the same de-Broglie wavelength, then the kinetic energy of the electron is


578) The curve drawn between velocity and frequency of photon in vacuum will be a


579) A potential difference of 42,000 volts is used in an X-ray tube to accelerate electrons. The maximum frequency of the X-raditions produced is


580) If the kinetic energy of the particle is increased by 16 times, the percentage change in the de Broglie wavelength of the particle is


581) Which of one is correct


582) Davisson and Germer experiment proved


583) A uniform electric field and a uniform magnetic field exist in a region in the same direction. An electron is projected with a velocity pointed in the same direction. Then the electron will be


584) Air becomes conducting when the pressure ranges between


585) Radiations of two photon’s energy, twice and ten times the work function of metal are incident on the metal surface successively. The ratio of maximum velocities of photoelectrons emitted in two cases is


586) Light of wavelength 5000 Å falls on a sensitive plate with photoelectric work functional of 1.9 eV. The kinetic energy of the photoelectron emitted will be


587) A beam of 35.0 keV electrons strikes a molybdenum target, generating the X-rays. What is the cut-off wavelength?


588) The wavelength of a 1 keV photon is 1.24 nm. The frequency of 1 MeV photon is


589) The minimum wavelength of X-ray emitted from X-ray machine operating at an accelerating potential of V volts is


590) The kinetic energy of an electron gets tripled, then the de-Broglie wavelength associated with it changes by a factor


591) In Milikan’s experiment, an oil drop having charge q gets stationary on applying a potential difference V in between two plates separated by a distance 'd'. The weight of the drop is


592) An electron of mass m and charge e initially at rest gets accelerated by a constant electric field E. The rate of change of de-Broglie wavelength of this electron at time t ignoring relativistic effects is


593) One electron and one proton is accelerated by equal potential. Ratio in their de-Broglie wavelength is


594) When a monochromatic point source of light is at a distance 0.2 m from a photoelectric cell, the saturation current and cut-off voltage are 12.0 mA and 0.5 V. If the same source is placed 0.4 m away from the photoelectric cell, then the saturation current and the stopping potential respectively are


595) The momentum of a charged particle moving in a perpendicular magnetic field depends on


596) The energy of a photon of green light of wavelength 50000 Å is


597) Dual nature of radiation is shown by


598) A photon will have less energy, if its


599) A metal plate gets heated when cathode rays strike against it due to


600) An X-ray tube is operated at 50 kV. The minimum wavelength produced is


601) De-Broglie wavelength of a body of mass 1 kg moving with velocity of 2000 m/s is


602) Gases begin to conduct electricity at low pressure because


603) When light falls on a metal surface, the maximum kinetic energy of the emitted photo-electrons depends upon


604) When ultraviolet rays are incident on metal plate, then photoelectric effect does not occur. It occurs by the incidence of


605) The kinetic energy of an electron with de-Broglie wavelength of 3 nm is