Title 25. Wave Optics.pdf ✅

1. In YDSE the separation between the slits is halved and the distance between slit and the screen is doubled. The fringe width is :- (1) unchanged (2) halved (3) doubled (4) four times 2. A polaroid is placed at 45° to an incoming linearly polarised light of intensity 0 I . Now the intensity of light passing through the polaroid after polarisation would be- (1) I0 (2) I0/2 (3) I0/4 (4) zero 3. A ray of light falls on a transparent glass slab with refractive index (relative to air) of 1.62. The angle of incidence for which the reflected and refracted rays are mutually perpendicular is :- (1) tan–1 (1.62) (2) sin–1 (1.62) (3) cos–1 (1.62) (4) none of these 4. The intensity ratio of the two interfering beams of light is . What is the value of 5 . Two waves having intensity I and 9I produce interference. If the resultant intensity at a point is 7I, what is the phase difference between the two waves? (1) 0° (2) 60° (3) 90° (4) 120° 6. Two slits separated by a distance of 1 mm, are illuminated with red light of wavelength 6.5×10–7m. The interference fringes are observed on a screen placed 1 m from the slits. Find the distance between the third dark fringe and the fifth bright fringe on the same side of the central maxima. (1) 1.625 mm (2)3.50 mm (3) 2.750 mm (4) None of the above 7. Wavelength of light used in a optical instrument are 1 = 4000 Å and 2=5000Å, then ratio of their respective resolving powers (corresponding to 1 and 2) is :- (1) 16 : 25 (2) 9 : 1 (3) 4 : 5 (4) 5 : 4 8. The angular fringe width does not depend upon :- (1) Wavelength () (2) Distance between slits (d) (3) Distance between slits and screen (D) (4) Ratio /d 9. When an unpolarised light of intensity 0 I is incident on a polarising sheet, the intensity of the light which does not get transmitted is :- 10. In a Young's double slit experiment, the separation between the two slits is d and the wavelength of the light is . The intensity of light falling on slit1 is four times the intensity of light falling on slit 2. Choose the correct choice(s). (a) If d = 0.99, the screen will contain only one maximum (b) If < d < 2, at least one more maximum (besides the central maximum) will be observed on the screen (c) If the intensity of light falling on slit 1 is reduced so that it becomes equal to that of slit2, the intensities of the observed dark and bright fringes will increase (c) If the intensity of light falling on slit 2 is increased so that it becomes equal to that of slit 1, the intensities of the observed dark and bright fringes will increase (1) a, b (2) a, c (3) b, c (4) b, d 11. In a Young's double slit experiment the intensity at a point where the path difference is ( 6   being the wavelength of the light used) is I. If 0 I denotes the maximum intensity, I/ 0 I is equal to :- Wave Optics
12. Young's double slit experiment is carried out by using green, red and blue light, one colour at a time. The fringe width recorded are ,   G R and ,  B respectively. Then 13. Four light waves are represented by (i) y = a1 sin t (ii) y = a2 sin (t +  ) (iii) y = a1 sin 2t (iv) y = a2 sin (2 t +  ) Interference fringes may be observed due to super position of (1) (i) and (ii), (iii) and (iv) (2) (i) and (iii), (iii) and (iv) (3) (ii) and (iv), (iii) and (iv) (4) (iii) and (iv) only 14. A Young's double slit experiment is performed with white light. (Choose the incorrect option) (1) The central fringe will be white (2) There will not be completely dark fringe (3) The fringe next to the central will be red (4) The fringe next to the central will be violet 15. If a thin mica sheet of thickness 't' and refractive index  = 5/3 is placed in the path of one of the interfering beams as shown in fig. then the displacement of the fringe system is – 16. In YDSE experiment, when two light rays make third minima, then they have:- (1) Phase difference of 3 (2) Phase difference of 5 2  (3) Path difference of 3 (4) Path difference of 5 2  17. In young's double-slit experiment, the intensity at a point is (1/4) of the maximum intensity. Angular position of this point is - (1) sin–1 (  /d) (2) sin–1 (  /2d) (3) sin–1 (  /3d) (4) sin–1 (  /4d) 18. The first minima due to a single slit diffraction is at  = 30° for a light of wavelength 5000 Å. The width of the slit is - (1) 5 × 10–5 cm (2) 1.0 × 10–4 cm (3) 2.5 × 10–5 cm (4) 1.25 × 10–5 cm 19. A slit of width 12 × 10–7 m is illuminated by light of wavelength 6000Ao. The angular width of the central maximum is approximately - (1) 30o (2) 60o (3) 90o (4) 0o 20. A calcite crystal is placed over a dot on a piece of paper and rotated. On seeing through the calcite, one will see - (1) one dot (2) two stationary dots (3) two rotating dots (4) one dot rotating about the other 21. The necessary condition for interference pattern of light is that light sources should be – (1) Of same amplitude, frequency, constant phase difference and of same state of polarization
(2) Of same amplitude, frequency but with varying phase difference and of same state of polarization (3) Of same frequency, constant phase difference and of different sate of polarisation (4) Of same amplitude, different frequency, constant phase difference and of same state of polarization 22. In Young's double slit experiment, the value of intensity at the site of constructive interference, should be equivalent to which of the following:- (1) Sum of intensities of both sources (2) Twice the sum of intensities of both sources (3) Difference of intensities of both sources (4) Four times the sum of intensities of both sources 23. The two coherent sources with intensity ratio  produce interference. The fringe visibility will be: 24. The main difference between the phenomena of interference and diffraction is that - (1) Diffraction is due to interaction of light from the same wave front, whereas interference is the interaction of waves from two separate sources. (2) Diffraction is due to superposition of light from the same wave front, whereas interference is due to two waves derived from the same source. (3) Diffraction is due to two waves derived from the same source, while interference is superposition of light from same wave front. (4) In both diffraction and interference, number of coherent the same sources is two 25. Diffraction effects are easier to notice in the case of sound waves than in the case of light waves because (1) sound waves are longitudinal (2) sound is precived by the ear (3) sound waves are mechanical waves (4) sound waves are of longer wavelength 26. Three waves of equal frequency having amplitudes10 m, 4 m, 7 m arrive at a given point with successive phase difference of /2, the amplitude the resulting wave in m is given by (1) 4 (2) 5 (3) 6 (4) 7 27. The graph showing the dependence of intensity of transmitted light on the angle between polarizer and analyser is (I0 is intensity of plane polarized light) 28. A diffraction pattern is obtained using a beam of red light. If the red light is replaced by the blue light, then (1) the diffraction pattern remains changed (2) diffraction bands become narrower and crowded together (3) bands become broader and farther apart (4) bands disappear 29. The distance between two coherent sources is0.1 mm. The fringe-width on a screen 1.2 m away from the source is 6.0 mm. The wavelength of light used is (1) 4000 Å (2) 5000 Å (3) 6000 Å (4) 7200 Å 30. When the angle of incidence on a material is 60o the reflected light is completely polarized. The velocity of refracted ray inside the material is :- 31. In YDSE setup, light of wavelength 640 nm is used with d = 0.8 mm and D = 1m. If intensity at central maximum is I0 and its position is y=0, then :- (1) Intensity at y = 0.4 mm is zero
(2) Intensity at y = 0.4 mm is 2 o I (3) Intensity at y = 0.4 mm is 2 o I (4) Intensity at y = 0.4 mm is I0 32 . Two coherent point sources s1 and s2 vibrating in phase emit light of wavelength  . The separation between the sources is 2  . The smallest distance from s2 on a line passing through s2 and perpendicular to s1 s2, where a minimum of intensity occurs is :- 33. Two polaroids are kept crossed to each other. Now one of them is rotated through an angle 45o .The percentage of incident light now transmitted through the system is :- (1) 15% (2) 25% (3) 50% (4) 60% 34. The distance between the first and the sixth minima in the diffraction pattern of a single slit is 0.5mm. The screen is 0.5m away from the slit. If the wavelength of light used is 0 5000 A , then the slit width will be. (1) 5 mm (2) 2.5 mm (3) 1.25 mm (4) 1.0 mm 35. In Young's double slit experiment, the seventh maximum with wavelength 1 is at a distance d1from central maxima and the same maximum with wavelength 2 is at a distance d2. Thend1/d2 :- (1) 1 2   (2) 2 1   (3) 2 1 2 2   (4) 2 2 2 1   36. At what angle should an un polarized beam be incident on a crystal of  = 3 , so that reflected beam is polarized :- (1) 45o (2) 60o (3) 90o (4) 0o 37. How will the diffraction pattern change when yellow light is replaced by blue light? The fringe will be :- (1) Wider (2) Narrower (3) Brighter (4) Fainter 38. 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 ? (1) The angular width of central maximum will be unaffected. (2) Diffraction pattern is not observed on the screen in the case of electrons. (3) The angular width of the central maximum of the diffraction pattern will increase. (4) The angular width of the central maximum will decrease. 39. In Young's double slit experiment, the slits are 2mm apart and are illuminated by photons of two wavelengths 0 1  =12000A and 0 2  =10000A . At what minimum distance from the common central bright fringe on the screen 2m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ? (1) 3 mm (2) 8 mm (3) 6 mm (4) 4 mm