Wave Optics PYQs Set 4 (PDF)

Set 4 of 9 · Questions 91-120 of 243

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Mere Teacher · Previous Year Questions NEET Physics · Wave Optics · Set 4 (Q91-120)
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91. $Two polaroide A and B are placed in such a way that the pass-axis of polaroids are perpendicular to each other. Now, another polaroid C is placed between A and B bisecting angle between them. If intensity of unpolarised light is I_{0} then intensity of transmitted light after passing through polaroid B will be :$ (1) $\frac{I _{0}}{4}$ (2) $\frac{I _{0}}{2}$ (3) $\frac{I _{0}}{8}$ (4) $Zero$ 92. $In Young's double slit experiment, 8^{th} maximum with wavelength ' λ_{1}' is at distance ' d_{1}' from the central maximum and 6^{th} maximum with wavelength ' λ_{2}' is at a distance ' d_{2} . Then \frac{d _{2}}{d _{1}} is$ (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) $\frac{4 λ _{2}}{3 λ _{1}}$ 93. $When monochromatic light of wavelength 600 nm is used in Young's double slit experiment, the fifth order bright fringe is formed at 6 mm from the central bright fringe on the screen. If the experiment is conducted with light of wavelength 400 nm from the central bright fringe, the third order bright fringe will be located at$ (1) $1.6 mm$ (2) $2 mm$ (3) $2.4 mm$ (4) $3 mm$ 94. $A beam of plane polarised light of large crosssectional area and uniform intensity of 3.3 Wm^{- 2} falls normally on a polariser (cross sectional area 3 \times 10^{- 4} m^{2} which rotates about its axis with an angular speed of 31.4 rad / s . The energy of light passing through the polariser per revolution, is close to$ (1) $1.0 \times 10^{- 5} J$ (2) $1.0 \times 10^{- 4} J$ (3) $5.0 \times 10^{- 5} J$ (4) $1.5 \times 10^{- 5} J$ 95. $A beam of unpolarized light passes through a tourmaline crystal A and then it passes through a second tourmaline crystal B oriented so that its principal plane is parallel to that of A . The intensity of emergent light is I_{0} . Now B is rotated by 45^{\circ} about the ray. The emergent light will have intensity (cos 45^{\circ} = \frac{1}{2})$ (1) $\frac{I _{0}}{2}$ (2) $\frac{l _{0}}{2}$ (3) $\frac{2}{I _{0}}$ (4) $\frac{2}{I _{0}}$ 96. $A beam of light of wavelength from a distant source falls on a single slit wide and the resulting diffraction pattern is observed on a screen away. The distance between the first dark fringes on either side of the central bright fringe is$ (1) $1.2 cm$ (2) $1.2 mm$ (3) $2.4 cm$ (4) $2.4 mm$ 97. $According to Huygens' principle, during refraction of light from air to a denser medium$ (1) $wavelength and speed increase$ (2) $wavelength decreases but speed increases$ (3) $wavelength and speed decrease$ (4) $wavelength increases but speed decreases.$ 98. $Width of one of the two slits in a Young's double slit interference experiment is half of the other slit. The ratio of the maximum to the minimum intensity in the interference pattern is:$ (1) $3 : 1$ (2) $(22 + 1) : (22 - 1)$ (3) $9 : 1$ (4) $(3 + 22) : (3 - 22)$ 99. $In a Fraunhoffer diffraction at a single slit, if yellow light illuminating the slit is replaced by blue light, then diffraction bands$ (1) $remain unchanged$ (2) $become wider$ (3) $disappear$ (4) $become narrower$ 100. $In the Young's double slit experiment the intensity produced by each one of the individual slits is I_{0} . The distance between two slits is 2 mm . The distance of screen from slits is 10 m . The wavelength of light is 6000 A^{\circ} . The intensity of light on the screen in front of one of the slits is____.$ (1) $I_{o} 2$ (2) $2 I_{o}$ (3) $4 I_{o}$ (4) $I_{o}$ 101. $Interference fringes are produced on a screen by using two light sources of intensities I and 9 I . The phase difference between the beams is \frac{π}{2} at point P and π at point Q on the screen. The difference between the resultant intensities at point P and Q is$ (1) $2 I$ (2) $4 I$ (3) $6 I$ (4) $8 I$ 102. $The relation I = I_{0} cos^{2} θ is (I_{0} - Intensity of incident light on the analyzer, I intensity of emergent light from the analyzer, θ - angle between plane of polarization and the axis of analyser)$ (1) $Newton's law$ (2) $Snell's law$ (3) $Brewster's law$ (4) $Malus's law$ 103. $In a Young's double slit experiment two slits are separated by 2 mm and the screen is placed one meter away.When a light of wavelength 500 nm is used, the fringe separation will be :$ (1) $0.75 mm$ (2) $0.50 mm$ (3) $1 mm$ (4) $0.25 mm$ 104. $In a Young's double slit experiment, the separation between the slits is 0.15 mm . In the experiment, a source of light of wavelength 589 nm is used and the interference pattern is observed on a screen kept 1.5 m away. The separation between the successive bright fringes on the screen is:$ (1) $5.9 mm$ (2) $3.9 mm$ (3) $1.9 mm$ (4) $2.3 mm$ 105. $In the Young's double slit experiment, the intensity of light passing through each of the two double slits is 2 \times 10^{- 2} W m^{- 2} . The screen. slit distance is very large in comparison with slit-slit distance. The fringe width is β . The distance between the central maximum and a point P on the screen is x = \frac{β}{3} . Then the total light intensity at that point is$ (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) $16 \times 10^{- 2} Wm^{2}$ 106. $For light diverging from a finite point source$ (1) $the wave front is parabolic$ (2) $the wave front is cylindrical$ (3) $the intensity at the wave front does not depend on the distance$ (4) $the intensity decreases in proportion to the distance squared.$ 107. $The value of numerical aperature of the objective lens of a microscope is 1.25 If light of wavelength 5000 A ° is used, the minimum separation between two points, to be seen as distinct, will be:$ (1) $0.24 μ m$ (2) $0.38 μ m$ (3) $0.12 μ m$ (4) $0.48 μ m$ 108. $The shape of wavefront of light diverging from point source$ (1) $spherical$ (2) $planar$ (3) $cylindrical$ (4) $circular$ 109. $If the two slits in Young's double slit experiment are of unequal width, then$ (1) $the bright fringes will have unequal spacing$ (2) $the bright fringes will have unequal brightness$ (3) $the fringes do not appear$ (4) $the dark fringes are not perfectly dark.$ 110. $When light propagates through a given homogeneous medium, the velocities of$ (1) $primary wave front are larger than those of secondary wavelets.$ (2) $primary wave fronts are lesser than those of secondary wavelets.$ (3) $primary wave fronts are greater than or equal to those of secondary wavelets.$ (4) $primary wave front and wavelets are equal.$ 111. $A plane wave front of wavelength λ is incident on a single slit of width a . The angular width of principal maximum is$ (1) $\frac{λ}{a}$ (2) $\frac{2 λ}{a}$ (3) $\frac{a}{λ}$ (4) $\frac{a}{2 λ}$ 112. $Critical angle for certain medium is sin^{- 1} (0.6) . The polarizing angle of that medium is$ (1) $tan^{- 1} [1.5]$ (2) $sin^{- 1} [0.8]$ (3) $tan^{- 1} [1.6667]$ (4) $tan^{- 1} [0.6667]$ 113. $The Young's double slit interference experiment is performed using light consisting of 480 nm and 600 nm wavelengths to form interference patterns. The least number of the bright fringes of 480 nm light that are required for the first coincidence with the bright fringes formed by 600 nm light is$ (1) $5$ (2) $4$ (3) $6$ (4) $8$ 114. $In a double-slit experiment, at a certain point on the screen the path difference between the two interfering waves is \frac{1}{8} th of a wavelength. The ratio of the intensity of light at that point to that at the center of a bright fringe is :$ (1) $0.568$ (2) $0.760$ (3) $0.853$ (4) $0.672$ 115. $If the ratio of the intensities of two waves producing interference is 49 : 16, then the ratio of the resultant maximum intensity to minimum intensity will be$ (1) $11 : 3$ (2) $49 : 16$ (3) $121 : 9$ (4) $7 : 4$ 116. $In a Young's double slit experiment, if the wavelength of light is increased by 50 % and the distance between the slits is doubled then the percentage change in fringe width is$ (1) $75$ (2) $50$ (3) $25$ (4) $15$ 117. $Visible light of wavelength falls normally on single slit and produces a diffraction pattern. It is found that the second diffraction minimum is at from the central maximum. If the first minimum is produced at , then is close to:$ (1) $25^{o}$ (2) $20^{o}$ (3) $30^{o}$ (4) $45^{o}$ 118. $The property of light which cannot be explained by Huygen's construction of wavefront is$ (1) $Refraction$ (2) $Reflection$ (3) $Diffraction$ (4) $Origin of spectra$ 119. $Young's double slit experiment is carried out by using green, red and blue light, one colour at a time. The fringe width recorded are β_{G}, β_{R}, β_{B} respectively, then$ (1) $β_{G} > β_{B} > β_{R}$ (2) $β_{B} > β_{G} > β_{R}$ (3) $β_{R} > β_{B} > β_{G}$ (4) $β_{R} > β_{G} > β_{B}$ 120. $If the source of light used in a Young's double slit experiment is changed from red to violet:$ (1) $the fringes will become brighter.$ (2) $consecutive fringe lineswill come closer.$ (3) $the central bright fringe will become a darkfringe.$ (4) $the intensity of minima will increase.$