**NEET AIPMT Physics Chapter Wise Solutions – Optics**

**1. A beam of light consisting of red, green and j blue colours is incident on a right angled prism. ; The refractive index of the material of the prism for the above red, green and blue wavelengths are 1.39, 1.44 and 1.47 respectively. (AlPMT 2015)**

(a) not separate the three colours at all

(b) separate the red colour part from the green and blue colours

(c) separate the blue colour part from the red and green colours

(d) separate all the three colours from one another

**2. At the first minimum adjacent to the central maximum of a single-slit diffraction pattern, the i phase difference between the Huygen’s wavelet from the edge of the slit and the wavelet from the midpoint of the slit is (aipmt 2015)**

(a) π radian

(b) π/8 radian

(c) π/4 radian

(d) π/2 radian

**3. In an astronomical telescope in normal adjustment a straight black line of length L is drawn on inside part of objective lens. The eye-piece forms a real image of this line. The length of this image is I. (Aipmt 2015)**

** The magnification of the telescope is**

**4. Two slits in Young’s experiment have widths in the ratio 1: 25. The ratio of intensity at the maxima and minima in the interference pattern, is I _{max}/I_{min} (Aipmt 2015)**

**5. For a parallel beam of monochromatic light of wavelength λ, diffraction is produced by a single slit whose width ‘a’ is of the ordcr of the wavelength of the light. If ‘D’ is the distance of the screen from the slit, the width of the central maxima will be (AlPMT 2015, Cancelled)**

**6. Two identical thin piano-convex glass lenses (refractive index 1.5) each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the centre. The intervening space is filled with oil of refractive index I .7. The focal length f the combination is (AIPMT 2015, Cancelled)**

(a) -50 cm

(b) 50 cm

(e) -20 cm

(d) -25 cm

**7. The refracting angle of a prism is A, and refractive index of the material of the prism is cot (A/2). The angle of minimum deviation is (AlPMT 2015, Cancelled)**

(a) 90° – A

(b) 180°+ 2 A

(c) 180° – 3A

(d) 180° – 2A

**8. In a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern? (AIPMT 2015, Cancelled)**

(a) 0.5 mm

(b) 0.02 mm

(c) 02 mm

(d) 0.1mm

**9. A beam of light of λ = 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is (AIPMT 2014)**

(a) 1.2 cm

(b) 1.2 mm

(c) 2.4 cm

(d) 2.4 mm

**10. In the Young’s double slit experiment, the intensity of light at a point on the screen where the path difference λ is K, (λ being the wavelength of light used). The intensity at a point where the path difference is λ/4 will be (AIPMT 2014)**

(a) K

(b) K /4

(c) K/2

(d) zero

**11. If the focal length of objective lens is increased then magnifying power of (AIPMT 2014)**

(a) microscope will increase but that of telescope decrease.

(b) microscope and telescope both will increase.

(c) microscope and telescope both will decrcasc.

(d) microscope will decrease but that of telescope will increase.

**12. The angle of a prism is A. One of its refracting surfaces is silvered. Light rays falling at an angle of incidence 2A on the first surface returns back through the same path after suffering reflection at the silvered surface. The refractive index μ, of the prism is (AIPMT 2014)**

(a) 2 sinA

(b) 2 cosA

(c) 1/2 cosA

(d) tanA

**13. A piano convex lens fits exactly into a piano concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices μ _{1} and μ_{2} and R is the radius of curvature of the curved surface of the lenses, then the focal length of the combination (NEET 2013)**

**14. In Young’s double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ _{1} = 12000 Å and λ_{2} = 10000 Å. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other? (NEET 2013)**

(a) 4 mm

(b) 3 m

(c) 8 mm

(d) 6mm

**15. For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging power of the eye lens behind the cornea is 20 D. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be (NEET 2013)**

(a) 1.67 cm

(b) 1.5 cm

(c) 5 cm

(d) 2.5 cm

**16. A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct? (NEET 2013)**

(a) The angular width of the central maximum will decrease.

(b) The angular width of the central maximum will be unaffected.

(c) Diffraction pattern is not observed on the screen in the case of electrons.

(d) The angular width of the central maximum of the diffraction pattern will increase.

**17. In Young’s double slit experiment the distance between the slits and the screen is doubled. The separation between the slits is reduced to half. As a result the fringe width (Karnataka NEET 2013)**

(a) is halved

(b) becomes four times

(c) remains unchanged

(d) is doubled

**18. A parallel beam of light of wavelength λ is incident normally on a narrow slit. A diffraction pattern formed on a screen placed perpendicular to the direction of the incident beam. At the second minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of slit is ( Karnataka NEET 2013)**

(a) 2π

(b) 3π

(c) 4π

(d) πλ

**19. The reddish appearance of the sun at sunrise and sunset is due to ( Karnataka NEET 2013)**

(a) the scattering of light

(b) the polarisation of light

(c) the colour of the sun

(d) the colour of the sky

**20. Two plane mirrors are inclined at 70°. A ray incident on one mirror at angle, θ after reflection falls on second mirror and is reflected from there parallel to first mirror. The value of θ is ( Karnataka NEET 2013)**

(a) 45°

(b) 30°

(c) 55°

(d) 50°

**21. When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index (Prelims 2012)**

(a) equal to that of glass

(b) less than one

(c) greater than that of glass

(d) less than that of glass

**22. A ray of light is incident at an angle of incidence i, on one face of a prism of angle A (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is μ, the angle of incidence i, is nearly equal to (prelims 2012)**

**23. A concave mirror of focal length f _{1}, is placed at a distance of d from a convex lens of focal length f_{2}. A beam of light coming from infinity and falling on this convex lens – concave mirror combination returns to infinity. The distance d must equal (prelims 2012)**

(a) f_{1} + f_{2}

(b) -f_{1} + f_{2}

(c) 2f_{1} + f_{2}

(d) -2f_{1} + f_{2}

**24. The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are (Prelims 2012)**

(a) 10 cm, 10 cm

(b) 15 cm, 5 cm

(c) 18 cm, 2 cm

(d) 11 cm, 9 cm

**25. For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index(Mains 2012)**

(a) lies between √2 and 1

(b) lies between 2 and √2

(c) is less than 1

(d) is greater than 2

**26. A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is (Mains 2012)**

(a) 10 cm

(b) 15 cm

(c) 2.5 cm

(d) 5 cm

**27. Which of the following is not due to total internal reflection? (Prelims 2011)**

(a) Working of optical fibre

(b) Difference between apparent and real depth of a pond

(c) Mirage on hot summer days

(d) Brilliance of diamond

**28. 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? (Prelims 2011)**

(a) Virtual, upright, height = 1 cm

(b) Virtual, upright, height = 0.5 cm

(c) Real, inverted, height = 4 cm

(d) Real, inverted, height = 1 cm

**29. A thin prism of angle 15° made of glass of refractive index μ _{1 }= 1.5 is combined with another prism of glass of refractive index μ_{2} = 1.75. The combination of the prisms produces dispersion without deviation. The angle of the second prism should be (Mains 2011)**

(a) 5°

(b) 7°

(c) 10°

(d) 12°

**30. A converging beam of rays is incident on a diverging lens. Having passed through the lens the rays intersect at a point 15 cm from the lens on the opposite side. If the lens is removed the point where the rays meet will move 5 cm closer to the lens. The focal length of the lens is (Mains 2011)**

(a) 5 cm

(b) -10 cm

(c) 20 cm

(d) -30 cm

**31. A ray of light travelling in a transparent medium of refractive index μ, falls on a surface separating the medium from air at an angle of incidence of 45°. For which of the following value of μ the ray can undergo total internal reflection? (Prelims 2010 )**

(a) μ = 1.33

(b) μ = 1.40

(c) μ = 1.50

(d) μ = 1.25

**32. A lens having foca) length f 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 (prelims 2010)**

**33. The speed of light in media M _{1} and M_{2} are 1.5 x 10^{8} m/s and 2.0 x 10^{8} m/s respectively. A ray of light enters from medium M_{1} to M_{2} at an incidence angle i. If the ray suffers total internal reflection, the value of i is (mains 2010)**

**34. A ray of light is incident on a 60° prism at the minimum deviation position. The angle of refraction at the first face (i.e., incident face) of the prism is (Mains 2010)**

(a) zero

(b) 30°

(c) 45°

(d) 60°

**35. Two thin lenses of focal lengths f and f are in contact and coaxial. The power of the combination is (prelims 2008)**

**36. A boy is trying to start a fire by focusing sunlight on a piece of paper using an equiconvex lens of focal length 10 cm. The diameter of the sun is 1.39 x 10 ^{9} m and its mean distance from the earth is 1.5 x 10^{11} m. What is the diameter of the sun’s image on the paper? (Prelims 2008)**

(a) 6.5 x 10

^{-5}m

(b) 12.4 x 10

^{-4}m

(c) 9.2 x 10

^{-4 }m

(d) 6.5 x 10

^{-4 }m

**37. A small coin is resting on the bottom of a beaker filled with liquid. A ray of light from the coin travels upto the surface of the liquid and moves along its surface. How fast is the light travelling in the liquid? (2007)**

(a) 2.4 x 10^{8} m/s

(b) 3.0 x 10^{8} m/s

(c) 1.2 x 1o^{8} m/s

(d) 1.8 x 10^{8} m/s.

**38. The frequency of a light wave in a material is 2 x 10’ Hz and wavelength is 5000 A. The refractive index of material will be (2007)**

(a) 1.50

(b) 3.00

(c) 1.33

(d) 1.40

**39. A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again? (2006)**

(a) 2 cm upward

(b) 1 cm upward

(c) 4.5 cm downward

(d) 1 cm downward.

**40. A convex lens 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 diopters of the combination is (2006)**

(a) zero

(b) 25

(c) 50

(d) infinite.

**41. The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 Å is of the order of (2005)**

(a) 10^{6} rad

(b) 10^{-2} rad

(c) 10^{-4} rad

(d) 10^{-6} rad.

**42. A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometre 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 Å, is of the order of (2004)**

(a) 0.5 m

(b) 5 m

(c) 5 mm

(d) 5 cm

**43. The refractive index of the material of a prism is √2 and its refracting angle is 30°. One of the refracting surfaces of the prism is made a mirror inwards. A beam of monochromatic light entering the prism from the other face will retrace its path after reflection from the mirrored surface if its angle of incidence on the prism is (2004)**

(a) 45°

(b) 60°

(c) 0°

(d) 30°

**44. A beam of light composed of red and green ray is incident obliquely at a point on the face of rectangular glass slab. When coming out on the opposite parallel face, the red and green ray emerge from (2004)**

(a) Two points propagating in two different non parallel directions

(b) Two points propagating in two different parallel directions.

(c) One point propagating in two different directions.

(d) One point propagating in the same directions.

**45. An equiconvex lens is cut into two halves along (2003)**

** (i) XOX’ and (ii) YOY’ as shown in the figure. Let f, f ‘,f ” be the focal lengths of the complete lens, of each half in case (i), and of each half in case (ii), respectively.**

** Choose the correct statement from the following**

**46. A convex lens is dipped in a liquid whose refractive index is equal to the refractive index of the lens. Then its focal length will (2003)**

(a) become zero

(b) become infinite

(c) become small, but non-zero

(d) remain unchanged

**47. 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 a distance d ahead of second wall, then required focal tength will be (2002)**

**48.Diameter of human eye lens is 2 mm. What will be the minimum distance between two points to resolve them, which are situated at a distance of 50 meter from eye. The wavelength of light is 5000 Å (2002)**

(a) 2.32 m

(b) 4.28 mm

(c) 1.25 cm

(d) 12.48 cm.

**49. For the given incident ray as shown in figure, the condition of total internal refraction of this ray the required refractive index of prism will be (2002)**

**50. Optical fibre are based on (2001)**

(a) total internal reflection

(b) less scattering

(c) refraction

(d) less absorption coefficient.

**51. A ray of light travelling in air have wavelength λ, frequency n, velocity v and intensity I. If this ray enters into water then these parameters are λ’, n’, v ‘ and I’ respectively. Which relation is correct from following? (2001)**

(a) λ = λ’

(b) n = n’

(c) v = v’

(d) I = I’

**52. A disc is placed on a surface of pond which has refractive index 5/3. A source of light is placed 4 m below the surface of liquid. The minimum radius of disc needed so that light is not coming out is, (2001)**

(a) ∞

(b) 3 m

(c) 6 m

(d) 4 m.

**53. A bubble in glass slab (μ = 1.5) when viewed from one side appears at 5 cm and 2 cm from other side, then thickness of slab is (2000)**

(a) 3.75 cm

(b) 3 cm

(c) 10.5 cm

(d) 2.5 cm.

**54. A tall man of height 6 feet, want to see his full image. Then required minimum length of the mirror will be (2000)**

(a) 12 feet

(b) 3 feet

(c) 6 feet

(d) any length.

**55. For a plano convex lens (μ = 1.5) has radius of curvature 10 cm. It is silvered on its plane surface. Find focal length after silvering (2000)**

(a) 10 cm

(b) 20 cm

(c) 15 cm

(d) 25 cm.

**56. Rainbow is formed due to (2000)**

(a) scattering and refraction

(b) internal reflection and dispersion

(c) reflection only

(d) diffraction and dispersion.

**57. A piano convex lens is made of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is (1999)**

(a) 200 cm

(b) 100 cm

(c) 50 cm

(d) 400 cm

**58. Colours appear on a thin soap film and on soap bubbles due to the phenomenon of (1999)**

(a) interference

(b) dispersion

(c) refraction

(d) diffraction

**59. If the refractive index of a material of equilateral prism is √3 , then angle of minimum deviation of the prism is (1999)**

(a) 60°

(b) 45°

(c) 30°

(d) 75°

**60. 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 upright image of the object coincident with it? (1998)**

(a) 50 cm

(b) 30 cm

(c) 12 cm

(d) 60 cm

**61. Light enters at an angle of incidence in a transparent rod of refractive index n. For what value of the refractive index of the material of the rod the light once entered into it will not leave it through its lateral face whatsoever be the value of angle of incidence? (1998)**

(a) n = 1.1

(b) n = 1

(c) n > √2

(d) n = 1.3

**62. An astronomical telescope of tenfold angular magnification has a length of 44 cm. The focal length of the objective is (1997)**

(a) 44 cm

(b) 440 cm

(c) 4 cm

(d) 40 cm.

**64. An electromagnetic radiation of frequency n, wavelength λ, travelling with velocity v in air, enters a glass slab of refractive index μ. The frequency, wavelength and velocity of light in the glass slab will be respectively (1997)**

**65. If a 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? (1996)**

(a) + 7.5 D

(b) – 0.75 D

(c) +6.5 D

(d) -6.5 D.

**66. The refractive index of water is 1.33. What will be the speed of light in water? (1996)**

(a) 4 x 10^{8} m/s

(b) 1.33 x 10^{8} m/s

(c) 3 x 10^{8} m/s

(d) 2.25 x 10^{8} m/s.

**67. A ray of light from a denser medium strikes a rare medium as shown in figure. The reflected and refracted rays make an angle of 90° with each other. The angles of reflection and refraction are r and r’. The critical angle would be (1996)**

**68. If f _{v} and f_{R} are the focal lengths of a convex lens for violet and red light respectively and F_{v}and F_{m} are the focal lengths of a concave lens for violet and red light respectively, then we must have (1996)**

**69. having a refractive index p. If c is the velocity of light in vacuum, the time taken by light to travel this thickness of glass is (1996)**

**70. A lens is placed between a source of light and a wall. It forms images of area A _{1} and A_{2} on the wall, for its two different positions. The area of the source of light is (1995)**

**71. Exposure time of camera lens at f/2.8 setting is 1/200 second. The correct time of exposure at f/5.8 is?**

(a) 0.20 second

(b) 0.40 second

(c) 0.02 second

(d) 0.04 second

**72. In a Fresnel biprism experiment, the two positions of lens give separation between the slits as 16 cm and 9 cm respectively. What is the actual distance of separation? (1995)**

(a) 13 cm

(b) 14 cm

(c) 12.5 cm

(d) 12 cm.

**73. Four lenses of focal length +15 cm and +150 cm are available for making a telescope. To produce the largest magnification, the focal length of the eyepiece should be (1994)**

(a) +15 cm

(b) +150 cm

(c) -150 cm

(d) -15 cm.

**74. The blue colour of the sky is due to the phenomenon of (1994)**

(a) scattering

(b) dispersion

(c) reflection

(d) refraction.

**75. Ray optics is valid, when characteristic dimensions are (1994, 89)**

(a) much smaller than the wavelength of light

(b) of the same order as the wavelength of light

(c) of the order of one millimetre

(d) much larger than the wavelength of light.

**76. A small source of light is 4 m below the surface of water of refractive index 5/3. In order to cut off all the light, coming out of water surface, minimum diameter of the disc placed on the surface of water is (1994)**

(a) 6 m

(b) o m

(c) 3 m

(d) 4 m.

**77. A parallel beam of monochromatic light of wavelength 5000 A is incident normally on a single narrow slit of width 0.001 mm. The light is focussed by a convex lens on a screen placed in focal plane. The first minimum will be formed for the angle of diffraction equal to (1993)**

(a) 0°

(b) 15°

(c) 30°

(d) 50°

**78. Interference was observed in interference chamber where air was present, now the chamber is evacuated, and if the same light is used, a careful I observer will see (1993)**

(a) no interference

(b) interference with brighter bands

(c) interference with dark bands

(d) interference with larger width

**79. Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is 3/2 is**

(a) 2 x 10^{-4} s

(b) 2 x 10^{8} s

(c) 2 x 10^{-11} s

(d) 2 x 10^{11} s

**80. There is a prism with refractive index equal to √2 and the refractive angle equal to 30°. One of the refractive surface of the prism is polished. A beam of monochromatic light will be retrace its path if its angle of indence over the refracting surface of the prism is (1992)**

(a) 0°

(b) 30°

(c) 45°

(d) 60°

**81. If yellow light emitted by sodium lamp in Young’s double slit expt is replaced by monochromatic blue of light of the same intensity**

(a) fringe width will decrease

(b) fringe width will increase

(c) fringe width will remain unchanged

(d) fringes will becomes less intense (1992)

**82. In Young’s double slit experiment carried out with light of wavelength (λ) = 5000 Å, the distance between the slits is 0.2 mm and the screen is at 200 cm from the slits. The central maximum is at x = 0. The third maximum (taking the central maximum as zeroth maximum) will be at x equal to (1992)**

(a) 1.67 cm

(b) 1.5 cm

(c) 0.5 cm

(d) 5.0 cm

**83. A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5. The wavelength of refracted light will be (1992, 91)**

(a) depend on intensity of refracted light

(b) same

(c) smaller

(d) larger

**84. Green light wavelength 5460 Å is inbident on an air-glass interface. If the refractive index of glass is 1.5, the wavelength of light in glass would be (c = 3 x 10 ^{8} ms^{-1}) (1991)**

(a) 3640 A

(b) 5460 A

(c) 4861 A

(d) none of these

**85. Ratio of intensities of two waves are given by 4: 1. Then ratio of the amplitudes of the two waves is (1991)**

(a) 2 : 1

(b) 1: 2

(c) 4:1

(d) 1:4

**86. In Young’s experiment, two coherent sources are placed 0.90 mm apart and fringe are observed one metre away. If it produces second dark fringe at a distance of 1 mm from central fringe, the wavelength of monochromatic light is used would be (1991)**

(a) 60 x 10^{-4} cm

(b) 10 x 10^{-4} cm

(c) 10 x 10^{-5} cm

(d) 6 x 10^{-5} cm

**87. In Young’s double slit experiment, the fringe width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4/3 , without disturbing the geometrical arrangement, the new fringe width will be (1990)**

(a) 0.30 mm

(b) 0.40 mm

(c) 0.53 mm

(d) 450 microns

**88. The Young’s double slit experiment is perfonned with blue and with green light of wavelengths 4360 Å and 5460 Å respectively. If x is the distance of 4th maxima from the central one, then (1990)**

**89. Interference is possible in (1989)**

(a) light waves only

(b) sound waves only

(c) both light and sound waves

(d) neither light nor sound waves

**90. A ray is incident at an angle of incidence i on one surface of a prism of small angle A and emerge normally from opposite surface. If the refractive index of the material of prism is μ, the angle of incidence i is nearely equal to (1989)**

**91. Which of the phenomenon is not common to sound and light waves ? (1988)**

(a) Interference

(b) Diffraction

(c) Coherence

(d) Polarisation

**92. Which one of the following phenomena is not explained by Huygen’s construction of wavefront ? (1988)**

(a) Refraction

(b) Reflection

(c) Diffraction

(d) Origin of spectra

**93. Focal length of a convex lens of refractive index 1.5 is 2 cm. Focal length of lens when immersed in a liquid of refractive index of 1.25 will be (1988)**

(a) 10 cm

(b) 2.5 cm

(c) 5 cm

(d) 7.5 cm

**ANSWERS**

**EXPLANATIONS**

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