Wave Optics PYQs Set 4 (PDF)

Set 4 of 10 · Questions 91-120 of 295

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Mere Teacher · Previous Year Questions JEE Main Physics · Wave Optics · Set 4 (Q91-120)
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91. $The head lights of a jeep are 1.2 m apart. If the pupil of the eye of an observer has a diameter of 2 mm and light of wavelength 5896Å is used, what should be the maximum distance of the jeep from the observer if the two head lights are just separated?$ (1) $33.9 km$ (2) $33.9 m$ (3) $3.39 km$ (4) $3.39 m$ 92. $When Young's double slit experiment is performed in air, the -coordinates of central maxima and maxima are and respectively. If the apparatus is immersed in a liquid of refractive index 1.5, the corresponding Y-coordinates will be$ (1) $2 cm, 7.5 cm$ (2) $3 cm, 6 cm$ (3) $2 cm, 4 cm$ (4) $\frac{4}{3} cm, \frac{10}{3} cm$ 93. $Blue light travelling in vacuum has a wavelength of . It enters a medium whose refractive index is 1.5 . What is its frequency in the medium?(Speed of light in vacuum )$ (1) $6.67 \times 10^{14} Hz$ (2) $10^{15} Hz$ (3) $- 4.45 \times 10^{14} Hz$ (4) $10^{14} Hz$ 94. $An unpolarised light is incident at an interface of two dielectric media having refractive indices of 2 (incident medium) and (medium) respectively. To satisfy the condition that reflected and refracted rays are perpendicular to each other, the angle of incidence is .$ (1) $45^{\circ}$ (2) $60^{\circ}$ (3) $10^{\circ}$ (4) $30^{\circ}$ 95. $When the same monochromatic ray of light travels through glass slab and through water, the number of waves in glass slab of thickness is same as in water column of height . If refractive index of glass is 1.5 then refractive index of water is$ (1) $1.258$ (2) $1.269$ (3) $1.286$ (4) $1.310$ 96. $Two sources are said to be coherent if they produce waves$ (1) $having a constant phase difference$ (2) $of equal wavelength$ (3) $of equal speed$ (4) $having same shape of wave front.$ 97. $In a Young's double slit experiment, the path difference, at a certain point on the screen, betwen two interfering waves is \frac{1}{8} th of wavelength. The ratio of the intensity at this point to that at the centre of a bright fringe is close to:$ (1) $0.74$ (2) $0.85$ (3) $0.94$ (4) $0.80$ 98. $In Young's double slit arrangement, slits are separated by a gap of 0.5 mm, and the screen is placed at adistance of 0.5 m from them. The distance between the first and the third bright fringe formed when the slitsare illuminated by a monochromatic light of 5890 ∖ AA is :-$ (1) $1178 \times 10^{- 9} m$ (2) $1178 \times 10^{- 6} m$ (3) $1178 \times 10^{- 12} m$ (4) $5890 \times 10^{- 7} m$ 99. $Consider the diffraction pattern obtained from the sunlight incident on a pinhole of diameter . If thediameter of the pinhole is slightly increased, it will affect the diffraction pattern such that:$ (1) $its size decreases, but intensity increases$ (2) $its size increases, but intensity decreases$ (3) $its size increases, and intensity increases$ (4) $its size decreases, and intensity decreases$ 100. $Due to Doppler's effect, the shift in wavelength observed is 0.1Å for a star producing wavelength 6000Å . Velocity of recession of the star will be$ (1) $5 km s^{- 1}$ (2) $25 km s^{- 1}$ (3) $20 km s^{- 1}$ (4) $10 km s^{- 1}$ 101. $The central fringe in the interference pattern obtained in Young's double slit experiment will be a dark fringe when the phase difference between the waves from the two slits is$ (1) $zero$ (2) $\frac{π}{2}$ (3) $π$ (4) $\frac{π}{3}$ 102. $A polarizer - analyzer set is adjusted such that the intensity of light coming out of the analyzer is just 10 % of the original intensity. Assuming that the polarizer-analyzer set does not absorb any light, the angle by which the analyzer need to be rotated further to reduce the output intensity to be zero is:$ (1) $60^{o}$ (2) $18.4^{o}$ (3) $45^{o}$ (4) $71.6^{o}$ 103. $Young's double slit inteference apparatus is immersed in a liquid of refractive index 1.44. Ithas slit separation of 1.5 mm. The slits are illuminated by a parallel beam of light whose wavelength in air is 690 nm. The fringe width on a screen placed behind the plane of slits at a distance of 0.72 m, will be:$ (1) $0.23 mm$ (2) $0.33 mm$ (3) $0.63 mm$ (4) $0.46 mm$ 104. $A microwave of wavelength falls normally on a slit of width . The angular spread of the central maxima of the diffraction pattern obtained on a screen away from the slit, will be:$ (1) $30^{\circ}$ (2) $15^{\circ}$ (3) $60^{\circ}$ (4) $45^{\circ}$ 105. $Two polaroide A and B are placed in such a way that the pass-axis of polaroids are perpendicular to each other. Now, another polaroid C is placed between A and B bisecting angle between them. If intensity of unpolarised light is I_{0} then intensity of transmitted light after passing through polaroid B will be :$ (1) $\frac{I _{0}}{4}$ (2) $\frac{I _{0}}{2}$ (3) $\frac{I _{0}}{8}$ (4) $Zero$ 106. $In Young's double slit experiment, 8^{th} maximum with wavelength ' λ_{1}' is at distance ' d_{1}' from the central maximum and 6^{th} maximum with wavelength ' λ_{2}' is at a distance ' d_{2} . Then \frac{d _{2}}{d _{1}} is$ (1) $\frac{3 λ _{1}}{4 λ _{2}}$ (2) $\frac{3 λ _{2}}{4 λ _{1}}$ (3) $\frac{4 λ _{1}}{3 λ _{2}}$ (4) $\frac{4 λ _{2}}{3 λ _{1}}$ 107. $When monochromatic light of wavelength 600 nm is used in Young's double slit experiment, the fifth order bright fringe is formed at 6 mm from the central bright fringe on the screen. If the experiment is conducted with light of wavelength 400 nm from the central bright fringe, the third order bright fringe will be located at$ (1) $1.6 mm$ (2) $2 mm$ (3) $2.4 mm$ (4) $3 mm$ 108. $A beam of plane polarised light of large crosssectional area and uniform intensity of 3.3 Wm^{- 2} falls normally on a polariser (cross sectional area 3 \times 10^{- 4} m^{2} which rotates about its axis with an angular speed of 31.4 rad / s . The energy of light passing through the polariser per revolution, is close to$ (1) $1.0 \times 10^{- 5} J$ (2) $1.0 \times 10^{- 4} J$ (3) $5.0 \times 10^{- 5} J$ (4) $1.5 \times 10^{- 5} J$ 109. $A beam of unpolarized light passes through a tourmaline crystal A and then it passes through a second tourmaline crystal B oriented so that its principal plane is parallel to that of A . The intensity of emergent light is I_{0} . Now B is rotated by 45^{\circ} about the ray. The emergent light will have intensity (cos 45^{\circ} = \frac{1}{2})$ (1) $\frac{I _{0}}{2}$ (2) $\frac{l _{0}}{2}$ (3) $\frac{2}{I _{0}}$ (4) $\frac{2}{I _{0}}$ 110. $A beam of light of wavelength from a distant source falls on a single slit wide and the resulting diffraction pattern is observed on a screen away. The distance between the first dark fringes on either side of the central bright fringe is$ (1) $1.2 cm$ (2) $1.2 mm$ (3) $2.4 cm$ (4) $2.4 mm$ 111. $According to Huygens' principle, during refraction of light from air to a denser medium$ (1) $wavelength and speed increase$ (2) $wavelength decreases but speed increases$ (3) $wavelength and speed decrease$ (4) $wavelength increases but speed decreases.$ 112. $Width of one of the two slits in a Young's double slit interference experiment is half of the other slit. The ratio of the maximum to the minimum intensity in the interference pattern is:$ (1) $3 : 1$ (2) $(22 + 1) : (22 - 1)$ (3) $9 : 1$ (4) $(3 + 22) : (3 - 22)$ 113. $In a Fraunhoffer diffraction at a single slit, if yellow light illuminating the slit is replaced by blue light, then diffraction bands$ (1) $remain unchanged$ (2) $become wider$ (3) $disappear$ (4) $become narrower$ 114. $In the Young's double slit experiment the intensity produced by each one of the individual slits is I_{0} . The distance between two slits is 2 mm . The distance of screen from slits is 10 m . The wavelength of light is 6000 A^{\circ} . The intensity of light on the screen in front of one of the slits is____.$ (1) $I_{o} 2$ (2) $2 I_{o}$ (3) $4 I_{o}$ (4) $I_{o}$ 115. $Interference fringes are produced on a screen by using two light sources of intensities I and 9 I . The phase difference between the beams is \frac{π}{2} at point P and π at point Q on the screen. The difference between the resultant intensities at point P and Q is$ (1) $2 I$ (2) $4 I$ (3) $6 I$ (4) $8 I$ 116. $The relation I = I_{0} cos^{2} θ is (I_{0} - Intensity of incident light on the analyzer, I intensity of emergent light from the analyzer, θ - angle between plane of polarization and the axis of analyser)$ (1) $Newton's law$ (2) $Snell's law$ (3) $Brewster's law$ (4) $Malus's law$ 117. $In a Young's double slit experiment two slits are separated by 2 mm and the screen is placed one meter away.When a light of wavelength 500 nm is used, the fringe separation will be :$ (1) $0.75 mm$ (2) $0.50 mm$ (3) $1 mm$ (4) $0.25 mm$ 118. $In a Young's double slit experiment, the separation between the slits is 0.15 mm . In the experiment, a source of light of wavelength 589 nm is used and the interference pattern is observed on a screen kept 1.5 m away. The separation between the successive bright fringes on the screen is:$ (1) $5.9 mm$ (2) $3.9 mm$ (3) $1.9 mm$ (4) $2.3 mm$ 119. $In the Young's double slit experiment, the intensity of light passing through each of the two double slits is 2 \times 10^{- 2} W m^{- 2} . The screen. slit distance is very large in comparison with slit-slit distance. The fringe width is β . The distance between the central maximum and a point P on the screen is x = \frac{β}{3} . Then the total light intensity at that point is$ (1) $8 \times 10^{- 2} W m^{- 2}$ (2) $4 \times 10^{- 2} W m^{- 2}$ (3) $2 \times 10^{- 2} W m^{- 2}$ (4) $16 \times 10^{- 2} Wm^{2}$ 120. $Two wavelengths λ_{1} and λ_{2} are used in Young's double slit experiment. λ_{1} = 450 nm and λ_{2} = 650 nm . The minimum order of fringe produced by λ_{2} which overlaps with the fringe produced by λ_{1} is n . The value of n is _____$