Practice Test


1) A ray of light falls spherical on mirror normally, the values of angle of incidence 'i' and angle of reflection 'r' respectively are


2) In an experiment to find the focal length of a concave mirror, an object is placed at a distance of 40 cm from it and forms image at 24 cm from the mirror, then the focal length is


3) An object is placed at a distance of 25 cm from a spherical mirror, its image is formed behind the mirror at a distance of 5 cm. The focal length and type of mirror is


4) A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Locate the image of the needle from the mirror.


5) An object is at a distance of 10 cm from a concave mirror and the image of the object is at a distance of 30 m from the mirror on the same side as that of the object. The radius of curvature of the concave mirror is


6) The lens formula with normal notation is given by


7) The lens marker's equation is given by


8) A concave lens has radii of curvatures of 20 cm and 30 cm respectively. If the refractive index of the material of lens is 1.6, its focal length is given by


9) The magnifying power of simple microscope, when image is formed at DDV, is ( where f is its focal length)


10) When the final image is formed at infinity, the magnifying power of compound microscope is ( using new cartesian sign conventions)


11) Which of the following is NOT an expression for magnifying power of compound microscope when final image is formed at distance of distinct vision ? ( using new cartesian sign conventions)


12) The length (L) of compound microscope when final image is formed at D.D.V is given by


13) Two thin lenses of power +12 D and -2D are combined together. Their equivalent focal length is


14) The length (L) of the astronomical telescope, for normal adjustment is


15) Magnifying power of an astronomical telescope is M.P. If the focal length of the eye-piece is doubled, then its magnifying power will be


16) Magnification of simple microscope when image at infinity is given by


17) The radius of curvature of each surface of a biconcave lens made up of glass of refractive index 1.5 is 30 cm. The focal length of the lens is


18) A convex lens of focal length f produces a real image 3 times as that of size of the object, the distance between the object and the lens is


19) Two thin lenses, one convex of focal length 10 cm and other concave lens are kept in contact to form a composite lens of focal length 130 cm. If the combination acts as a converging lens then the focal length of second lens is


20) Light is a form of energy which travels as


21) The straight path of the light is called


22) The study of light without considering diffraction is called


23) The bending of light round the edge of an obstacle is called


24) Light from point source travels in a straight line with very high speed hence


25) Choose the COORECT statement.


26) The geometrical centre of surface of spherical mirror is called its


27) The principal axis of spherical mirror passes through


28) After reflection, the parallel beam of light appears to come from a point then the type of mirror is


29) Which spherical mirror is divergent ?


30) For the spherical mirrors, the relation between focal length (f) and radius of curvature ( R ) is given by


31) A convex mirror gives an image which is


32) A concave mirror produces a virtual image when the object is


33) An object is placed at a distance equal to focal length of a convex mirror. If the focal length of a miror be f, then the distance image from the pole of the mirror is


34) A concave mirror is placed on a horizontal table with its axis vertically upwards. Let O be the pole of the mirror and C be the centre of curvature. A point object placed at C, forms real image at C. If the mirror is now filled with water, the image will be


35) The field of view is maximum for


36) For concave mirror, if the object is at the focus point F, the image is


37) According to new cartesian sign convention, the distances measured


38) A virtual image larger than the object can be produced by


39) A convex mirror may be used for all but it can NOT be used for


40) Given a point source of light, which of the following can produce a parallel beam of light ?


41) A virtual object is placed between the pole and principal focus of a convex mirror produces an image which is


42) While deriving expression for refraction at single curved surface, the object is considered as


43) The focal length of a lens depends upon


44) The focal length of concave lens, according to new cartesian sign conventions is


45) According to new cartesian sign convention, all the distances are measured from


46) A diverging lens may NOT have


47) A concave lens of focal length f produces an image 1/4 of the size of the object, the object should be kept at ____ from the lens.


48) An object is kept at 0.2 m from a convex lens of focal length 0.15 m. The position of the image is


49) A beam of light is incident on a convex lens parallel to its principal axis. As one moves away from the optical centre of the lens on its other side, the intensity of light


50) A screen is placed 90 cm from an object. The image of the object on the screen is formed by a convex lens at two different locations seperated by 20 cm. The focal length of the lens is


51) A single lens which will form the image of a given object at the same point as is formed by the combination of two or more thin lenses, is called as


52) Two thin lenses may be combined so as to


53) Two thin covering lenses of focal length 15 cm and 30 cm are held in contact with each other. The focal length of the combination is


54) The least distance of distinct vision for a young adult with normal vision is


55) A normal eye is unable to see objects at a distance less than distance of distinct vision. It is because


56) The clarity of image formed on retina of eye depends on the


57) A convex lens of short focal length held very close to the eye, to observe minute objects clearly is called as


58) The magnifying power of simple microscope is maximum when image is formed at


59) When a convex lens of 2.5 cm focal length is used as a magnifying glass, normal eye can see an object clearly at a distance of 25 cm. The magnifying power of the instrument is


60) The magnifying power of simple microscope is 6 when the image is formed at distance of distinct vision (25 cm) from its optical centre. The focal power of the simple microscope in dioptre is


61) The compound microscope is used to see


62) Compound microscope has an object of comparitively.


63) Compound microscope is NOT used in


64) In a compound microscope, the intermediate image is


65) The focal length of the eye piece of compound microscope is


66) A compound microscope has a magnifying power of 35. Assume that the final image is formed at DDV (25 cm). If the focal length of eye piece is 8 cm, the magnification produced by objective is


67) The objects which are at large distance as compared to the focal length of the lens ( greater than 10 x f) are reffered as


68) The objective of astronomical telescope has


69) The intermediate image formed by the objective is


70) To see terrestrial objects, the final image must be


71) When a ______ is introduced between objective and eye piece of telescope then it is used as a terrestrial telescope.


72) When astronomical telescope is adjusted for normal adjustment the final image is formed at


73) The focal length of objective and eye piece of astronomical telescope are 2 m and 5 cm respectively. The magnifying power of telescope when final image is formed at infinity is


74) The objective of reflecting telescope is


75) A ______ is fixed at focal point of the objective, which reflects the collected rays to eye piece.


76) Out of the following optical instruments which one is independent of chromatic and spherical aberrations


77) A fly is sitting on the objective of a telescope pointed to the moon. What is the effect in the photograph of the moon taken through the telescope ?


78) The distance between an object and the screen is 75 cm. When a convex lens of focal length 12 cm is placed in between the object and the screen,magnification of real image formed can be ( magnitude only)


79) Ray optics is valid, when characteristic dimensions are


80) A diminished virtual image can be produced only with


81) A converging lens is used to form an image on a screen. When the upper half of the lens is covered by an opaque screen, then


82) The lens will be visible in vacuum when the refractive index of the lens is


83) A lens behaves as a converging lens in air and a diverging lens in water. The refractive index of the material is ( refractive index of water is 1.33)


84) A person using a lens as a simple microscope sees an


85) When we view object of height 15 m with a telescope of magnifying power 10. To him, the object appears


86) The magnifying power of simple microscope is


87) An optical instrument, in general, extends our range of vision by


88) In astronomical telescope, which of the following statement is NOT applicable ?


89) For observing fainter distant objects and for high resolving power following instrument telescope is used


90) An astronomical telescope of ten fold angular magnification has length of 44 cm. The focal length of objective is


91) When two thin lenses are kept in contact, the focal length of the combination is


92) In case of reflection from curved surface


93) If the object is placed at A and the image is formed at B when the rays are refracted through a convex lens. The positions of A and B are changeable, such pair of points is called


94) The wavelength range of visible light is


95) When an object is kept in front of a convex lens, the distance between it and the real image is 54 cm. If the magnification produced is 2, the focal length of the lens is


96) A vessel is filled with two different liquids which do not mix. One is 40 cm deep and has R. I. 1.6 and other is 30 cm deep and has R. I. 1.5. The apparent depth of vessel when viewed normally is


97) An air bubble inside a cubical block of glass of side 4.5 cm seems to be at 2 cm from one face and 1 cm from the other face opposite to first when viewed normally. The real distance of bubble is (from first face)


98) If the R. I. of water is 4/3 and that of glass slab is 5/3, then the critical angle for the ray coming from glass to water is


99) A ray of light enters from a denser medium into rarer medium. The speed of light in rarer being twice that in the denser. The angular range in which the fish just below the surface of denser can see the objects outside is


100) Critical angle of light passing from glass to air is minimum for


101) A ray of light is incident from denser to rarer. The reflected and refracted ray are at right angle to each other. If r is the angle of reflection and r' is the angle of refraction, then critical angle is


102) R. I. of water is 4/3 and a fish inside the water judges the height of the bird above the water level as 200 m, then the actual height above the water level is


103) A ray of light is incident from a small source 4 m below the surface of water of R. I. 5/3. In order to cut all the light coming out of water the minimum diameter of disc placed on water surface is


104) Just before the time of sunset, the sun appears to be elliptical because


105) The distance of object when a concave mirror produces an image of magnification `m`


106) The distance of object when a convex produce an image of magnification `m`


107) The image formed by a convex mirror of focal length 30 cm is one quarter of the size of object. The distance of object from the mirror is


108) An object is placed at the focus of concave mirror of focal length 20 cm. The distance of the image is


109) A concave mirror of focal length f in air is used in a transparent liquid of R. I. 2 for producing an image of the object. What is its new focal length?


110) A lens with + P power is immersed in water. Its power


111) A convex lens produces a real image m times the size of the object. The distance of the object is


112) A convex lens of focal length f produces a virtual image n times of the object. The distance of object is


113) The distance between the object and real image formed by a convex lens is D. If the the magnification is m, then focal length f is


114) In the displacement method if the distance between object and screen is D, the real images are formed corresponding to two positions of the lens separated by 'd'. The ratio of sizes of the two images is


115) A concave and convex lens have same focal length of 20 cm and are put in contact. The combination is used to view an object of 5 cm length kept at 20 cm from the lens combination. As compared to object the image will be


116) The resolution limit of eye is one minute. At a distance x km from the eye two objects are situated with 3 m separation. For the two objects to be just resolved the value of x for the eye is


117) A plano - convex lens of R. I. 1.5 silvered at the convex surface behaves as a concave mirror of focal length 20 cm. What is the radius of curvature of curved surface?


118) An empty spherical flask of diameter 30 cm is placed in water of R. I. 4/3. A parallel beam of light strikes the flask. Where does it get focused when observed from within the flask?


119) A plano-convex lens has a focal length of 20 cm and R. I. 1.5. What is its radius of curvature?


120) The radius of curvature of each surface of a double convex lens is 20 cm and R. I. of its material is 3/2. The lens is cut into two equal parts along a line perpendicular to the principal axis. What is the focal length of either of the new lens?


121) The radius of curvature of each surface of a double convex lens is 20 cm and R. I. of its material is 3/2. The lens is cut into two equal parts along a line perpendicular to the principal axis. What is the focal length of each part?


122) When a convex lens of focal length 10 cm is placed in contact with a concave lens, the power of combination is + 5 D. What will be the power when the lenses are separated by 10 cm in air?


123) A thin converging lens forms the image of a certain object magnified m times. The magnification becomes n, when lens is moved nearer to object by a distance x. Focal length of the lens is


124) In displacement method if D is the distance of the object and screen and 'd' is the separation between the two positions of the lens, then the ratio of magnified image to that of the object is


125) A thin lens has a focal length f and its aperture has diameter d. It forms an image of intensity I, the central part up to diameter d/2 is blocked by an opaque paper. The focal length and the image intensity will change to


126) A spherical mirror forms an erect image three times the size of the object. If the distance between the object and the image is 100 cm the focal length of the mirror is


127) A square wire of side 6.0 cm is placed 25.0 cm away from a concave mirror of focal length 10.0 cm. The area enclosed by the image of the wire, whose center is on the principal axis, is


128) The focal length of a concave mirror is f and the distance from the object to the principal focus is x, then ratio of the size of the image to the size of the object is


129) The dispersive powers of the materials of the two lenses are in the ratio 4/3. If the achromatic combination of these two lenses in contact is a convex lens of focal length 60.0 cm, then focal length of component lenses is


130) Indicate the colour which travels through glass with the minimum speed


131) In an achromatic combination of prisms the net deviation produced when the prisms are of the same material, is


132) Two lenses of focal lengths + 10 and -15 cm are in contact. For zero chromatic aberration, the ratio of dispersive powers is


133) A convex lens has mean focal length 30 cm and the dispersive power of the material is 40. The longitudinal chromatic aberration for the object at infinity is


134) A parallel beam of white light falls on a convex lens. Images of blue, yellow and red light are formed on the other side of the lens at a distance 20 cm, 20.5 cm and 21.4 cm respectively. The dispersive powers of the material of the lens will be


135) For a myopic eye, the far point is at 250 cm. To correct this defect, the nature of the lens and its focal length will be


136) A person cannot see objects clearly beyond 50 cm. The power of the lens to correct his vision is


137) A far-sighted person cannot focus clearly on an object closer than 120 cm. If he wants to read a book at a distance 40 cm, he requires a lens of


138) The far point of the myopic eye is 200 cm. The power of the lens required to correct this defect is


139) A person can see objects lying between 50 cm and 100 cm. What power of lens will be use for reading a book? (Distance of L.D.V. is 25 cm)


140) A myopic person can see things clearly lying between 8 cm and 100 cm from his eyes. The lens which enables his to see the moon should have a focal length of


141) A convex lens of 3 cm focal length is used as a simple microscope by an eye with distance of least distinct vision as 30 cm. What is the magnifying power?


142) The objective and eye-piece of a compound microscope have focal length 0.4 cm and 2.5 cm respectively. If the lengths of the tube is 16 cm and distance of distinct vision is 25 cm, the magnifying power of microscope giving final image at infinity is


143) Resolving power of a microscope can be increased if we use


144) The distance between objective and eye-piece for astronomical telescope when adjusted for parallel rays is 80 cm, the magnification is 15. The focal lengths of two lenses are


145) The powers of the lenses of a telescope are 0.5 and 20 dioptres. Its magnifying power is


146) The objective and eye-lens of a telescope have focal lengths 30 cm and 3 cm. It is focused on a scale 2 metres away. The distance between the two lenses for normal vision is


147) A small object is placed at a distance of 3.6 cm from a magnifier of focal length 4.0 cm. The linear magnification is


148) A small object is placed at a distance of 3.6 cm from a magnifier of focal length 4.0 cm. The angular magnification is nearly (D = 25 cm)


149) A compound microscope is used to enlarge an object kept at a distance of 0.03 m from the objective which consists of several convex lenses in contact and has the focal length 0.02 m. The image formed by objective is at


150) A locality is photographed from an aeroplane flying at a height of 3 km with a camera whose focal length is 1 m. The ratio of the linear size of the image to the size of the object is nearly


151) The resolution limit of eye is 1 minute. At a distance X km from the eye two person stand with a lateral separation of 3 m. For the two persons to be just resolved by eye, X should be


152) A person looks at two different trees in an open space. First tree is 2 meters high at a distance of 50 meters and second tree is 4 meters high at a distance of 200 meters respectively from the eye. The apparent sizes are


153) The maximum value of index of refraction of a material of a prism which allows the passage of light through it when the refracting angle of prism is A, is


154) A rod of length 10.0 cm lies along the principal axis of a concave mirror of focal length in such a way that the end closer to the pole is 20.0 cm away from it. The length of the image is


155) A luminous object is placed at a distance of 30 cm from a convex lens of focal length 20 cm. On the other side of lens, at what distance from the lens, a convex mirror of radius of curvature 10 cm be placed in order to have an inverted image of the object coincident with it?


156) A convex lens has different media on its two sides. Its first focal length is 10 cm. An object is placed at a distance of 15 cm from the first principal focus. The lens produces its image on the other side at a distance of 20 cm from the second principal focus. The second focal length is


157) A convex lens of focal length f is placed some-where in between the object and a screen. The distance between object and screen is x. If magnification produced is m, the focal length of the lens is


158) The principal section of a glass prism is an isosceles triangle ABC with AB = AC. The face AC is silvered. A ray is incident normally on face AB and after two reflection, it emerges from the face BC, per-pendicular to it. The angle BAC of the prism is


159) A magnifying glass is made of combination of convex lens of power + 20 D and concave lens of power 4 D. If the distance of distinct vision of eye is 25.0 cm, the magnifying power of the lens, when image is formed at infinity is


160) An angular magnification of 30 is desired using an objective of focal length 1.25 cm and eye piece of focal length 5.0 cm. To set up the microscope the distance between the lenses is approximately


161) A simple two lens telescope has an objective of focal length 2.5 cm. The telescope is pointed at an object at a very large distance which subtends an angle of 1 milliradian on the naked eye. The eye piece is so adjusted that final image is formed at infinity. The size of the real image formed by objective is


162) A small telescope has an object lens of focal length 140 cm and eye piece of focal length 5.0 cm. The telescope is used to view a 100 m tall tower 3 km away. The height of the image of the tower formed by objective lens is


163) A man stands on a vertical tower of height 20 m. Calculate the distance upto which he will be able to see on the surface of earth. Neglect height of man. Radius of earth = 6400 km.


164) A rectangular block of glass is placed on a printed page lying on a horizontal plane. Find the minimum value of refractive index of glass for which the letters on the page are not visible from any of the vertical faces of the block


165) The distance between two point sources of light is 24 cm. Where should a convergent lens of focal length 9 cm be placed between them to obtain images of both sources at the same point?


166) One face of rectangular glass slab of thickness 6 cm is silvered. An object is held 8 cm in front of the front face forms an image 10 cm behind the silvered face. What is refractive index of glass?


167) The focal length of a lens in a camera, marked f : 2.8 is 8 cm. What is diameter of lens?


168) If the correct time of exposure is 1/200 s with a lens marked f : 2.8, what would be correct time of exposure with a lens marked f : 5.6?


169) The area of moon's image produced by a convex lens is proportional to focal length as


170) A glass sphere with center O is shown in fig. AOB and COD are two diameters at right angle to each other. A ray parallel to AOB strikes the sphere at P. Find the deviation of ray as it emerges out of the sphere.


171) An object is placed 20 cm the left of a convex lens of focal length 10 cm. If a concave mirror of focal length 5 cm is placed 30 cm to the right of the lens, find the magnification


172) A plano-convex lens when silvered on the plane side behaves like a concave mirror of focal length 30 cm. When silvered on convex side, it behaves like a concave mirror of focal length 10 cm. The refractive index of material is


173) A point object is placed on the principal axis of convex lens of focal length 20 cm at a distance 40 cm to the left on it. The diameter of the lens is 10 cm. If the eye is placed 60 cm to the right of the lens at a distance h below the principal axis, then max. value of h to see the image is


174) The length of a microscope is 14 cm and its magnifying power is 25 for relaxed eye. The focal length of the eyes lens is 5 cm. The distance of the object from the objective is


175) A student can distinctly see the object upto a distance 15 cm. He wants to see the black board at a distance of 3 m. Focal length and power of lens used respectively will be


176) Two thin lenses of powers 12 D and - 2 D respectively are placed in contact, the power, focal length and nature respectively will be


177) For a normal eye, the least distance of distinct vision is nearly


178) For a myopic (short-sighted) eye, rays from far distant objects are brought to focus at a point


179) Myopia occurs due to


180) In hypermetropia i.e., long-sightedness, the person can


181) To correct short-sightedness we require


182) The long-sigtedness is corrected by using


183) A man suffering from myopia can read a paper placed at 10 cm. What king of lens will he use for reading a book at 30 cm?


184) The least distance of distinct vision for a person with defective eye-sight is 100 cm. What kind of lens will he use to see clearly an object at 25 cm?


185) The interior of the eye is coated with transparent membrane and is provided with nerve, it is called


186) A myopic person can see things clearly which lie between 8 cm and 100 cm from his eyes. His near point with the correcting lens will be


187) A long-sighted person has a least-distance of distinct vision of 50 cm. He wants to reduce it to 25 cm. He should use a


188) The ability of eye to focus on both near and far objects is called


189) A cylindrical lens is required to correct


190) Loss of the eye to focus on both far and near objects with advancing age is


191) The eye is most sensitive, with ordinary intensity, for the colours


192) A person with one eye has a


193) In human eye the focusing is done by


194) The resolving power of human eye is


195) The light which enters the human eye experiences most of its refraction while passing through


196) A person is 6 ft. tall. How tall must be a vertical mirror if he is able to see his entire length?


197) Rainbow is formed due to combination of


198) When a ray of light enters a glass slab, then


199) Ratio of intensities of two waves is 9 : 1. If these waves are superimposed, what is ratio of max. and min. intensities?


200) A doctor tells a patient to use spectacles with convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is power of combination?


201) What is the minimum height of a plane mirror held vertically in front of a man of 6 ft. tall to see his entire image?


202) A ray of light containing both red and blue light is incident on the refracting surface of a prism, then


203) Optical fibre is based on


204) Blue colour of sky is due to phenomenon of


205) When light is passed through a prism, the colour which deviates least is


206) Newton gave the corpuscle theory on the basis of


207) A bulb is located on a wall. Its image is to be obtained on a parallel wall with the help of convex lens. The lens is placed at distance d ahead of second wall, then required focal length will be


208) Which is having minimum wavelength?


209) What is the cause of Greenhouse effect?


210) Light propagates linearly due to its


211) Brilliance of diamond is due to


212) The Cauchy's dispersion formula is


213) What is the path difference for destructive interference?


214) Velocity of light is equal to


215) Why sun has elliptical shape when it rises and sets? IT is due to


216) If convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power?


217) Why laser rays are used to measure long distance?


218) A man is standing in a room of mirror. Man is able to see how many of his images in mirror when he is seeing at a corner?


219) Optic fibres are related with


220) Which of the following electromagnetic wave have highest wavelength?


221) If an interference pattern has maximum and minimum intensity in the ratio of 36 : 1, then what will be the ratio of amplitude?


222) A convex lens is dipped in a liquid of refractive index equal to the refractive index of the lens. Then its focal length will


223) When a beam of light is used to determined the position of an object, the maximum accuracy is achieved if the light is


224) An astronaut is looking down on earth's surface from a space shuttle at an altitude of 400 km. Assuming that the astronaut's pupil diameter is 5 mm and the wavelength of visible light is 500 nm, the astronaut will be able to receive linear objects of the size of about


225) A convex lens is immersed in oil then refractive index depends upon


226) Huygen's wave theory of light could not explain


227) An optical illusion which occurs usually in deserts on hot summer days is based on


228) Prof. C. V. Raman was awarded the Nobel prize for


229) Which of the following does not change when light goes from one medium to another?


230) For obtaining equal and same height, mirror should be


231) The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image.


232) A beam of light is composed of red and green rays and is incident obliquely at a point on face of a rectangular glass slab. When coming out of the opposite parallel face, the red and green rays emerge from


233) A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometer from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 A, is of the order of


234) In order to obtain a real image of magnification 2 using a converging lens of focal length 20 cm, where should be an object be placed?


235) Assertion : A red object appears dark in the yellow light.
Reason : The red colour is scattered less.


236) Assertion : At the first glance, the top surface of the Morpho butterfly's wing appears a beautiful blue-green. If the wing moves the colour changes.
Reason : Different pigments in the wing reflect light at different angles.


237) Assertion : A famous painting was painted by not using brush strokes in the usual manner, but rather a myriad of small colour dots. In this painting changes as you move away.
Reason : The angular separation of adjacent dots changes with the distance from the painting.


238) An endoscope is employed by a physician to view the internal parts of a body organ. It is based on the principle of


239) When a compat disc is illuminated by a source of white light, coloured lines are observed. This is due to


240) A point object is placed at the center of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is


241) The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 A is of order


242) When exposed to sunlight thin films of oil on water often exhibit colours due to phenomenon of


243) In case of linearly polarised light, the magnitude of electric vector


244) In refraction, light waves are bent on passing from one medium to other, because in second medium


245) A telescrope has objective lens of focal length 200 cm and eye piece of focal length 2 cm. If this telescope is used to see a 50 m tall building at a distance of 2 km what is height of image of building formed by objective lens?


246) A stone thrown in still water, creates a circular wave patterns moving radially outwards. If r is distance measured from the center of pattern, the amplitude of wave varies is


247) Which of the following statement is true?


248) A convex and a concave lens, each having same focal length of 25 cm are put in contact to form a combination of lenses. The power in diapoters of the combination is


249) A microscope is focused on a mark on a piece of paper. A slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How would be microscope be moved to get the mark focus again?


250) A lens of power +2 diopters is placed in contact with a lens of power - 1 diopter. The combination will behave like


251) A convex lens of crown glass (n = 1.525) will behave as a divergent lens if immersed in


252) Magnifying power of a compound microscope is the ratio of angle formed by the final image to the angle formed by the object when


253) A magnifying glass is to be used at the fixed object distance of 1 inch. If it is to produce an erect image magnified 5 times its focal length should be


254) The penetration of light into the region of geometric shadow is called


255) A convex mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be


256) A convex lens of focal length 0.5 m and concave lens of focal length 1 m are combined. The power of the resulting lens will be


257) Fraunhofer spectrum is a


258) The refractive index of water with respect to air is 4/3 and the refractive index of glass with respect to air is 3/2. The refractive index of water with respect of glass of


259) A person cannot see objects clearly beyond 2.0 m. The power of lens required to correct his vision will be


260) An astronomical telescope has an angular magnification of magnitude 4 for distance objects. The separation between the objective and the eye piece is 36 cm and final image is formed at infinity. The focal lengths of the objective and eye-piece are respectively.


261) The unit of luminous efficiency of electric bulb is


262) The interference phenomenon can take place


263) The focal length of an equi-convex lens in air is equal to tither of its radii of curvature. The refractive index of the material of the lens is


264) Lux is a unit of


265) A watch shows time as 8:35 when seen through a mirror, time appears will be


266) A luminous object is placed at a distance of 30 cm from the convex lens of focal length 20 cm. On the other side of the lens, at what distance from the lens a convex mirror of radius of curvature 10 cm be placed in order to have an up-right image of the object coincident with it


267) A point source of light is placed 4 m below the surface of water of refractive index 5/3. The minimum diameter of a disc which should be placed above the source on the surface of water to cut-off all light coming out of water is


268) The focal length of the objective and eye lenses of a telescope are respectively 200 cm and 5 cm. The maximum magnifying power of the telescope will be


269) A polariser is used to


270) A person having normal vision is able to just resolve two poles separated by a distance of 1 m. The distance of the poles from the person is


271) A convex lens of focal length 40 cm is combined with a concave lens of focal length 40 cm and placed in contact. The focal power of the combination is


272) If Young's experiment with one source of light and two slits be performed so that interfering beam traverse in water instead of air


273) Young's double slit experiment is performed with 500 nm light, slit separation 1 mm and screen distance 1 m. A and B are bright bands and C is a dark band. The distance AB is


274) A ray of unpolarised light is incident on a glass plate at the polarising angle. Then


275) A glass slab of thickness 4 cm contains the same number of waves as 5 cm of water when both are traversed by the same monochromatic light. If the refractive index of water is 4/3, what is that of glass?


276) You are looking through an illuminated spectrometer slit. When the width of the slit is decreased, you will find


277) A blue cross on a white background illuminated with white light is observed through a red filter. What is seen?


278) In a terrestrial telescope, the focal lengths of objective, inverting lens and eye lens are 90 cm, 5 cm and 6 cm respectively. Then for relaxed vision, the minimum length of the tube will be


279) To increase the resolving power of a microscope


280) The energy of a visible photon is of the order of


281) When a ray of light enters a glass slab from air


282) We have a source of red light and a blue light of same power. Then the red light gives photons per second


283) Focal length of a convex lens will be maximum for


284) If the distance of the far point for a myopia patient is doubled, the focal length of the lens required to cure it will become


285) Light is incident at an angle i and refracts to an angle r into a glass plate of uniform thickness t. The lateral displacement of incident ray at emergence is


286) Two nicol prisms (polariser and analyser) have their axes at angle 60 degrees in between. If I is the intensity of light falling on first nicol, then that of emerging light from the second nicol is


287) A blue object on a white background when seen through a blue filter will appear


288) In Young's double slit experiment the width of one slit is double that of the other. The ratio of intensity of a bright band to that of a dark band in the interference pattern produced by them, is


289) An observer looks at a tree of height 15 m with a telescope of magnifying power 10. To him the tree appears


290) A concave mirror of focal length f produces an image, n times the size of the object. If the image is real, then the distance of the object from the mirror is


291) When the length of a microscope increases its magnifying power


292) If the luminous intensity of a unidirectional bulb is 100 candela, then total luminous flux emitted from the bulb is


293) A convex - concave lens has faces of radii 3 cm and 4 cm respectively and is made of glass of refractive index 1.6. Its focal length is


294) Two coherent sources of intensity ratio 9 : 4 produces interference. What is the ratio between the maxima and minima in the interference pattern produces by them?


295) A diffraction grating has 5000 lines / cm . The maximum order visible with wavelength 6000 A is


296) The image formed by a convex mirror of focal length 30 cm is a quarter of the size the object. The distance of the object from the mirror is


297) Two lenses are placed in contact with each other and the focal length of combination is 80 cm. If the focal length if one is 20 cm, then the power of the other will be


298) The focal length of an objective and eye lens are 120 cm and 6 cm respectively. If the angle subtended by an object situated at far point on the objective is 2', then for relaxed vision the angle subtended by an image on objective will be


299) A set of letters which have been coloured are kept below a plane glass slab, which of the coloured letter will appear the most raised above others


300) The full image of an object is formed on the screen by a convex lens. If now an opaque object covers half of the lens then


301) There is an interference because of two waves of intensity I each, then the maximum intensity obtained is


302) For the largest distance of the image from a convex mirror of focal length 10 cm, the object should be kept at


303) The refractive indices of glass and water with respect to air are 3/2 and 4/3 respectively the refractive index of glass with respect to water will be


304) A divergent lens will produce


305) If the position of objective lens and eye piece lens are interchanged in a microscope, then the instrument will be have as


306) A long sighted person has a minimum distance of distinct vision of 50 cm. He wants to reduce it to 25 cm. He should use a


307) In a young's double slit experiment, the separation between the slits is d and the distance of the screen from the slits is D. The adjacent bright fringes are separated by a distance y. When D and d are simultaneously doubled, the fringes separation becomes


308) The radii of curvature of a thin double convex lens is 15 cm and 10 cm respectively. If the refractive index of the material is 1.5, the focal length of the lens will be


309) As astronomical telescope has an objective of focal length 100 cm and diameter 10 cm. Its eye piece is of focal length 5 cm and of diameter 2 cm. With the telescope in normal adjustment, the angular magnification is


310) A convex lens of focal length 40 cm is in contact with a concave length of focal length 25 cm the power of the combination in diopters is


311) In a Young's double slit experiment using red and blue lights of wavelengths 600 nm and 480 nm respectively, the value of n for which the red fringe coincides with (n + 1) th blue fringe is


312) Which of the following cannot be polarised?


313) Two waves have their amplitudes in the ratio of 1 : 9. The maximum and minimum intensities when they interface are in the ratio


314) In a Young's double slit experiment, the source illuminating the slits its changed from blue to violet. The width of the fringes


315) A satisfactory photographic print is obtained when the exposure time is 10 secs at a distance of 2 m from a 60 cd lamp. The time of exposure required for the same quality print at a distance of 4 m from a 120 cd lamp.


316) Polarization of light takes place due to many processes. Which of the following will not cause polarization?


317) In a compound microscope, the intermediate image is


318) In a vessel of depth 15 cm, liquid is poured till the liquid level appears to be at half the depth, the liquid level is 5 cm from the top. Calculate the refractive index of the liquid


319) When the complete Young's double slit apparatus is immersed in water, the fringes


320) In Young's double slit experiment the separation between the slits is halved and distance between the slits and the screen is doubled. The fringe width is


321) A lens having focal length and aperture of diameter d forms an image of intensity I . Aperture of diameter d/2 in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively


322) Which of the following is not due to total internal reflection?


323) A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following options describe best the image formed of an object of height 2 cm placed 30 cm from the lens?