Wave Optics PYQs Set 2 (PDF)

Set 2 of 10 · Questions 31-60 of 295

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Mere Teacher · Previous Year Questions JEE Main Physics · Wave Optics · Set 2 (Q31-60)
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31. $In a Young's double slit experiment, if the slit separation is twice the wavelength of light used, then the maximum number of interference maxima is$ (1) $0$ (2) $3$ (3) $5$ (4) $7$ 32. $Red light of wavelength 625 nm is incident normally on an optical diff raction grating with 2 \times 10^{5} lines / m . Including central principal maxima, how many maxima may be observed on a screen which is far from the grating?$ (1) $15$ (2) $17$ (3) $8$ (4) $16$ 33. $In Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength λ = 500 nm is incident on the slits. The total number of bright fringes that are observed in the angular range - 30º < θ < 30º is:$ (1) $320$ (2) $641$ (3) $640$ (4) $321$ 34. $In Young's double slit experiment the distance between the slits and the screen is 1.2 m and the distance between the two slits is 2.4 mm . If a thin transparent mica sheet of thickness 1 μ m and R.I. 1.5 is introduced between one of the interfering beams, the shift in the position of central bright fringe is$ (1) $0.125 mm$ (2) $0.25 mm$ (3) $2 mm$ (4) $0.5 mm$ 35. $Two coherent sources of intensity ratio α interfere. In interference pattern \frac{I _{max} - I _{min}}{I _{max} + I _{min}} =$ (1) $\frac{2 α}{1 + α}$ (2) $\frac{2 α}{1 + α}$ (3) $\frac{2 α}{1 + α}$ (4) $\frac{1 + α}{2 α}$ 36. $In a Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength λ = 500 nm is incident on the slits. The total number of bright fringes that areobserved in the angular range - 30^{\circ} \leq θ \leq 30^{\circ} is$ (1) $640$ (2) $320$ (3) $321$ (4) $641$ 37. $In Young's double slit experiment, the fringe width is 2 mm . The separation between the 13^{th} bright fringe and the 4^{th} dark fringe from the centre of the screen on same side will be$ (1) $13 mm$ (2) $17 mm$ (3) $19 mm$ (4) $23 mm$ 38. $When two light waves each amplitude ' A' and having a phase difference of \frac{π}{2} superimposed then the amplitude of resultant wave is$ (1) $\frac{A}{2}$ (2) $2 A$ (3) $2 A$ (4) $\frac{A}{2}$ 39. $The width of the diffraction band varies$ (1) $inversely as the wavelength$ (2) $directly as the width of the slit$ (3) $directly as the distance between the slit and the screen$ (4) $inversely as the size of the source from which the slit is illuminated.$ 40. $Angular width of central maximum of a diffraction pattern due to a single slit does not depend upon$ (1) $Distance between slit and source$ (2) $Wavelength of light used$ (3) $Width of the slit$ (4) $Frequency of light used$ 41. $In Young's double slit experiment, the two slits are ' d' distance apart. Interference pattern is observed on the screen at a distance ' D' from the slits. First dark fringe is observed on the screen directly opposite to one of the slits. The wavelength of the light is$ (1) $\frac{d ^{2}}{D}$ (2) $\frac{D ^{2}}{d}$ (3) $\frac{d ^{2}}{2 D}$ (4) $\frac{D ^{2}}{2 d}$ 42. $In a Young's double slit experiment, the slits are separated by 0.2 mm. If the slits separation is increased to 0.4 mm, the percentage change of the fringe width is:$ (1) $25 %$ (2) $50 %$ (3) $0 %$ (4) $100 %$ 43. $If white light is used in the Newton's rings experiment, the colour observed in the reflected light is complementary to that observed in the transmitted light through the same point. This is due to$ (1) $90^{\circ} change of phase in one of the reflected waves$ (2) $180^{\circ} change of phase in one of the reflected waves$ (3) $145^{\circ} change of phase in one of the reflected waves$ (4) $45^{\circ} change of phase in one of the reflected waves.$ 44. $The luminous border that surrounds the profile of a mountain just before sun rises behind it, is an example of$ (1) $dispersion$ (2) $total internal reflection$ (3) $interference$ (4) $diffraction.$ 45. $A polarized light of intensity I_{0} is passed through another polarizer whose pass axis makes an angle of 60^{\circ} with the pass axis of the former. What is the intensity of emergent polarized light from second polarizer?$ (1) $I = I_{0} /5$ (2) $I = I_{0}$ (3) $I_{0} /4$ (4) $I = I_{0} /6$ 46. $Two monochromatic light beams have intensities in the ratio 1 : 9 . An interference pattern is obtained by these beams. The ratio of the intensities of maximum to minimum is$ (1) $8 : 1$ (2) $4: 1$ (3) $3: 1$ (4) $9 : 1$ 47. $The angular width of a fringe in a double slit experiment is found to be on a screen away. The wavelength of light used is . The change in angular width of the fridge if the entire measurement system is immersed in water is [Use refractive index of water as ]$ (1) $0.05^{\circ}$ (2) $0.10^{\circ}$ (3) $0.15^{\circ}$ (4) $0.20^{\circ}$ 48. $Two light waves having the same wavelength in vacuum are in phase initially. Then the first wavetravels a path through a medium of refractive index while the second wave travels a path of length through a medium of refractive index . After this the phase difference between the two waves is$ (1) $\frac{2 π}{λ} (n_{2} L_{1} - n_{1} L_{2})$ (2) $\frac{2 π}{λ} (\frac{L _{1}}{n _{1}} - \frac{L _{2}}{n _{2}})$ (3) $\frac{2 π}{λ} (n_{1} L_{1} - n_{2} L_{2})$ (4) $\frac{2 π}{λ} (\frac{L _{2}}{n _{1}} - \frac{L _{1}}{n _{2}})$ 49. $On placing a thin film of mica of thickness in the path of one of the interfering beams in Young's double slit experiment using monochromticlight, the fringe patternshifts through a distance equal to the width of bright fringe. If , the refractive index of mica is$ (1) $1.1$ (2) $1.3$ (3) $1.5$ (4) $1.4$ 50. $When light of an unknown polarization is examined with a polaroid, it is found to exhibit maximum intensity I_{0} along y -axis and minimum intensity \frac{2 I _{0}}{3} along x -axis. The intensity transmitted through a polaroid with pass axis at 45^{\circ} to y -axis (in x - y plane) is$ (1) $\frac{5 I _{0}}{8}$ (2) $\frac{I _{0}}{2}$ (3) $\frac{5 I _{0}}{6}$ (4) $\frac{I _{0}}{4}$ 51. $From Brewster's law, except for polished metallic surfaces, the polarising angle$ (1) $depends on wavelength and is different for different colours$ (2) $independent of wavelength and is different for different colours$ (3) $independent of wavelength and is same for different colours$ (4) $depends on wavelength and is same for different colours$ 52. $In Young's double slit experiment, using monochromatic light of wavelength λ, the intensity of light at a point on the screen where path difference is λ is K units. The intensity of light at a point where path difference is λ /3 is$ (1) $4 K$ (2) $K$ (3) $2 K$ (4) $K /4$ 53. $The diffraction fringes obtained by a single slit are of$ (1) $equal width$ (2) $equal width and unequal intensity$ (3) $unequal width but equal intensity$ (4) $unequal width and unequal intensity.$ 54. $A parallel beam of monochromatic light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the first minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of the slit is$ (1) $zero$ (2) $\frac{π}{2}$ (3) $π$ (4) $2 π$ 55. $In Young's double slit experiment, slits are separated by 2 mm and the screen is placed at a distance of 1.2 m from the slits. Light consisting of two wavelengths 6500Å and 5200Å are used to obtain interference fringes. Then the separation between the fourth bright fringes of two different patterns produced by the two wavelengths is$ (1) $0.312 mm$ (2) $0.123 mm$ (3) $0.213 mm$ (4) $0.412 mm$ 56. $In Young's double slit experiment with sodium vapour lamp of wavelength 589 nm and the slits 0.589 mm apart, the half angular width of the central maximum is$ (1) $sin^{- 1} 0.01$ (2) $sin^{- 1} 0.0001$ (3) $sin^{- 1} 0.001$ (4) $sin^{- 1} 0.1$ 57. $Monochromatic light of wavelength 500 nm is used in Young's double slit experiment. An interference pattern is obtained on a screen. When one of the slits is covered with a very thin glass plate (refractive index ), the central maximum is shifted to a position previously occupied by the bright fringe. The thickness of the glass-plate is________ .$ 58. $In a Young's double slit experiment 15 fringes are observed on a small portion of the screen when light of wavelength 500 nm is used. Ten fringes are observed on the same section of the screen when another light source of wavelength λ is used Then the value of λ is (in nm)$ 59. $In Young's double slit experiment, carried out with light of wavelength 5000 ∖ AA, the distance between the slits is 0.3 mm and the screen is at 200 cm from the slits. The central maximum is at x = 0 cm . The value of x for third maxima is____ mm .$ 60. $In Young's double slit experiment, monochromatic light of wavelength 5000Å is used. The slits are 1.0 mm apart and screen is placed at 1.0 m away from slits. The distance from the centre of the screen where intensity becomes half of the maximum intensity for the first time is_______\times 10^{- 6} m$