109 Chapter Ray and Wave Optics 1. An astronomical telescope has a large aperture to [2002] reduce spherical aberration have high resolution increase span of observation have low dispersion. 2. If two mirrors are kept at 60 to each other, then the number of images formed by them is [2002] 5 6 7 8 3. Electromagnetic waves are transverse in nature is evident by [2002] polarization interference reflection diffraction 4. Wavelength of light used in an optical instrument are λl = 4000 Å and λ2= 5000Å, then ratio of their respective resolving powers (corresponding to λ1 and λ2) is [2002] 16: 25 9: 1 4: 5 5: 4 Ans: 5. Which of the following is used in optical fibres? [2002] total internal reflection scattering diffraction refraction. 6. Consider telecommunication through optical fibres. Which of the following statements is not true? [2003] Optical fibres can be of graded refractive index Optical fibres are subject to electromagnetic interference from outside Optical fibres have extremely low transmission loss Optical fibres may have homogeneous core with a suitable cladding. 7. To demonstrate the phenomenon of interference, we require two sources which emit radiation [2003] of nearly the same frequency of the same frequency of different wavelengths of the same frequency and having a definite phase relationship Ans: 8. The image formed by an objective of a compound microscope is [2003] virtual and diminished real and diminished real and enlarged virtual and enlarged Ans: 9. To get three images of a single object, one should have two plane mirrors at an angle of [2003] 60 90 120 30 10. [2004] 11. A plano convex lens of refractive index 1.5 and radius of curvature 30 cm. Is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of size of the object [2004] 60 cm 30 cm 20 cm 80 cm Ans: 12. The angle of incidence at which reflected light is totally polarized for reflection from air to glass (refractive index n), is [2004]
110 tan 1 (1/ n) sin 1 (1/ n) sin 1 tan 1 Ans: 13. The maximum number of possible interference maxima for slit-separation equal to twice the wavelength in Young s double-slit experiment is [2004] three five infinite zero 14. An electromagnetic wave of frequency r = 3.0 MHz passes from vacuum into a dielectric medium with permittivity = 0.4. Then [2004] wave length is halved and frequency remains unchanged wave length is doubled and frequency becomes half wave length is doubled and the frequency remains unchanged wave length and frequency both remain unchanged. 15. A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4/3 and the fish is 12 cm below the surface, the radius of this circle in cm is [2005] 16. Two point white dots are 1 mm apart on a black paper. They are viewed by eye of pupil diameter 3 mm. Approximately, what is the maximum distance at which these dots can be resolved by the eye? (Take wavelength of light = 500 nm) [2005] 1 m 5 m 3 m 6 m 17. A thin glass (refractive index 1.5) lens has optical power of 5 D in air. Its optical power in a liquid medium with refractive index 1.6 will be [2005] 1D 1 D 25 D 25 D 18. 18. A Young s double slit experiment uses a monochromatic source. The shape of the interference fringes formed on a screen is [2005] circle hyperbola parabola straight line Ans: 19. If I0 is the intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity when the slit width is doubled? [2005] 4 I0 2 I0 I0 /2 I0 20. When an unpolarized light of intensity I0 is incident on a polarizing sheet, the intensity of the light which does not get transmitted is [2005] 1/4 I0 1/2 I0 I0 zero 21. The refractive index of a glass is 1.520 for red light and 1.525 for blue light. Let D1 and D2 be angles of minimum deviation for red and blue light respectively in a prism of this glass. Then, [2006] D1 < D2 D1 = D2 D1 can be less than or greater than D2 depending upon the angle of prism D1 > D2 22. [2007]
111 23. Two lenses of power 15 D and +5 D are in contact with each other. The focal length of the combination is [2007] + 10 cm 20 cm 10 cm + 20 cm Ans: 24. Ans: 25. A student measures the focal length of a convex lens by putting an object pin at a distance u from the lens and measuring the distance v of the image pin. The graph between u and v plotted by the student should look like [2008] [2008] Ans: 26. An experment is performed to find the refractive index of glass using a travelling microscope. In this experiment distances are measured by [2008] a vernier scale provided on the microscope a standard laboratory scale a meter scale provided on the microscope a screw gauge provided on the microscope 27. A mixture of light, consisting of wavelength 590 nm and an unknown wavelength, illuminates Young s double slit and gives rise to two overlapping interference patterns on the screen. The central maximum of both lights coincide. Further, it is observed that the third bright fringe of known light coincides with the 4th bright fringe of the unknown light. From this data, the wavelength of the unknown light is: [2009] 885.0 nm 442.5 nm 776.8 nm 393.4 nm
112 28. [2009] medium of refractive index μ (I) = μ0 + μ2 I, where μ0 and μ2 are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. Q. The initial shape of the wavefront of the beam is [2010] convex concave convex near the axis and concave near the periphery planar Ans: 32. Directions: Question are based on the following paragraph. An initially parallel cylindrical beam travels in a medium of refractive index μ (I) = μ0 + μ2 I, where μ0 and μ2 are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. Q. The speed of light in the medium is [2010] minimum on the axis of the beam the same everywhere in the beam directly proportional to the intensity I maximum on the axis of the beam 33. Ans: 29. In an optics experiment, with the position of the object fixed, a student varies the position of a convex lens and for each position, the screen is adjusted to get a clear image of the object. A graph between the object distance u and the image distance v, from the lens, is plotted using the same scale for the two axes. A straight line passing through the origin and making an angle of 45 with the x-axis meets the experimental curve at P. The coordinates of P will be: [2009] (f/2, f/2) (f, f) (4 f, 4 f) (2 f, 2 f) Ans: 30. Directions: Question are based on the following paragraph. An initially parallel cylindrical beam travels in a medium of refractive index μ (I) = μ0 + μ2 I, where μ0 and μ2 are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. Q. As the beam enters the medium, it will [2010] diverge converge diverge near the axis and converge near the periphery travel as a cylindrical beam 31. Directions: Question are based on the following paragraph. An initially parallel cylindrical beam travels in a [2011] 45 60 75 30 34. This question has a paragraph followed by two statements, Statement 1 and Statement 2. Of the given four alternatives after the statements, choose the one that describes the statements. A thin air film is formed by putting the convex surface of a plane-convex lens over a plane glass plate. With monochromatic light, this film gives an interference pattern due to light reflected from the top (convex) surface and the bottom (glass plate) surface of the film. Statement 1: When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of π. Statement 2: The centre of the interference pattern is dark. [2011] Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1. Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1. Statement 1 is false, Statement 2 is true.
113 Statement 1 is true, Statement 2 is false. 35. A car is fitted with a convex side-view mirror of focal length 20 cm. A second car 2.8 m behind the first car is overtaking the first car at a relative speed of 15 m/s. The speed of the image of the second car as seen in the mirror of the first one is: [2011] 1/15 m/s 10 m/s 15 m/s 1/10 m/s 36. At two points P and Q on screen in Young s double slit experiment, waves from slits S1 and S2 have a path difference of 0 and λ/4, respectively. The ratio of intensities at P and Q will be: [2011] 2: 1 2 :1 4: 1 3: 2 37. In a Young s double slit experiment, the two slits act as coherent sources of wave of equal amplitude A and wavelength λ. In another experiment with the same arrangement the two slits are made to act as incoherent sources of waves of same amplitude and wavelength. If the intensity at the middle point of the screen in the first case is I1 and in the second case is I2, then the ratio I1/I2 is [2011] 2 1 0.5 4 38. A beaker contains water up to a height h1 and kerosene of height h2 above water so that the total height of (water + kerosene) is (h1 + h2). Refractive index of water is μ1 and that of kerosene is μ2. The apparent shift in the position of the bottom of the beaker when viewed from above is [2011] increase decrease remain same does not depend on colour of light 40. Statement - 1: On viewing the clear blue portion of the sky through a Calcite Crystal, the intensity of transmitted light varies as the crystal is rotated. Statement - 2: The light coming from the sky is polarized due to scattering of sun light by particles in the atmosphere. The scattering is largest for blue light. [2011] Statement -1 is true, statement-2 is false. Statement-1 is true, statement-2 is true, statement-2 is the correct explanation of statement-1 Statement-1 is true, statement-2 is true, statement-2 is not the correct explanation of statement-1 Statement-1 is false, statement-2 is true. 41. [2012] 42. 39. When monochromatic red light is used instead of blue light in a convex lens, its focal length will [2011] [2012]
114 Ans: 43. An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind the lens. A glass plate 1 cm thick, of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object shifted to be in sharp focus of film? [2012] 7.2 m 2.4 m 3.2 m 5.6 m Ans: 7. 8. 9. 1. 10. 2. 3. 4. 11. 12. 5. 6. 13.
115 14. 17. 15. 18. 16. 19. 20. 21.
116 22. 25. 23. 26. 24. 27.
117 29. 28. 30. 31.
118 32. 36. 33. 37. 34. 35.
119 41. 38. 39. 40. 42.
120 43.