Wave Optics PYQs Set 8 (PDF)

Set 8 of 9 · Questions 211-240 of 243

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Mere Teacher · Previous Year Questions NEET Physics · Wave Optics · Set 8 (Q211-240)
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211. $Consider a tank made of glass (refractive index 1.5) with a thick bottom. It is filled with a liquid of refractive index µ. A student finds that, irrespective of what the incident angle i (see figure) is for a beam of light entering the liquid, the light reflected from the liquid glass interface is never completely polarized. For this to happen, the minimum value of µ is:$ (1) $\frac{5}{3}$ (2) $\frac{4}{3}$ (3) $\frac{3}{5}$ (4) $\frac{5}{3}$ 212. $Young's double slit experiment gives interference fringes of width . A thin glass plate made of material of refractive index 1.5 is kept in the path of light from one of the slits, then the fringe width becomes$ (1) $zero$ (2) $0.45 mm$ (3) $0.3 mm$ (4) $0.15 mm$ 213. $In an experiment, light passing through two slits separated by a distance of 0.3 mm is projected on to a screen placed at 1 m from the plane of slits. It is observed that the distance between the central fringe and the adjacent bright fringe is 1.9 mm . The wavelength of light in nm is$ (1) $450$ (2) $495$ (3) $530$ (4) $570$ 214. $Two coherent sources O_{1} and O_{2} in Young's double slit experiment are illuminated with monochromatic light of wavelength 5000Å . If a second order dark fringe is formed at a point R on the screen, the path difference O_{1} R \sim O_{2} R is$ (1) $7.5 μ m$ (2) $0.75 μ m$ (3) $0.075 μ m$ 215. $Two identical light waves having phase difference φ propagate in same direction. When they superpose, the intensity of resultant wave is proportional to$ (1) $cos^{2} ϕ$ (2) $cos^{2} \frac{ϕ}{2}$ (3) $cos^{2} \frac{ϕ}{3}$ (4) $cos^{2} \frac{ϕ}{4}$ 216. $The box of a pin hole camera, of length L, has hole of radius a. it is assumed that when the hole is illuminated by a parallel beam of light of wavelength the spread of the spot (obtained on the opposite wall of the camera) is the sum of its geometrical spread and the spread due to diffraction. The spot would then have its minimum size (say ) when :$ (1) $a = λ L and b_{min} = (\frac{2 λ ^{2}}{L})$ (2) $a = λ L and 4 λ L$ (3) $a = \frac{λ ^{2}}{L} and b_{min} = 4 λ L$ (4) $a = \frac{λ ^{2}}{L} and b_{min} = (\frac{2 λ ^{2}}{L})$ 217. $The question has a paragraph followed by two statements, Statement-1 and Statement-2. Of the given four alternatives after the statements, choose the one that describes the statements. [Geometrical Optics] A thin air film is formed by putting the convex surface of a plane-convex lens over a plane glass plate. With monochromatic light, this film gives an interference pattern due to light reflected from the top (convex) surface and the bottom (glass plate) surface of the film. Statement -1 : When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of π Statement -2 : The centre of the interference pattern is dark.$ (1) $Statement-1 is true, statement-2 is false.$ (2) $Statement-1 is true, Statement-2 is true, Statement-2 is the correct explanation of Statement-1$ (3) $Statement-1 is true, Statement-2 is true, Statement-2 is not the correct explanation of Statement-1$ (4) $Statement-1 is false, Statement-2 is true$ 218. $Which of the following are true for a single slit diffraction?(A) Width of central maxima increases with increase in wavelength keeping slit width constant.(B) Width of central maxima increases with decrease in wavelength keeping slit width constant.(C) Width of central maxima increases with decrease in slit width at constant wavelength.(D) Width of central maxima increases with increase in slit width at constant wavelength.(E) Brightness of central maxima increases for decrease in wavelength at constant slit width.$ (1) $(A) (C) (E) only$ (2) $(A) (D) only$ (3) $(B) (D) only$ (4) $(B) (C) only$ 219. $Given below are two statements : Statement I : In a Young's double slit experiment, the angular separation of fringes will increase as the screen is moved away from the plane of the slits Statement II: In a Young's double slit experiment, the angular separation of fringes will increase when monochromatic source is replaced by another monochromatic source of higher wavelength. In the light of the above statements, choose the correct answer from the options given below :$ (1) $Both Statement I and Statement II are false$ (2) $Statement I is false but Statement II is true$ (3) $Both Statement I and Statement II are true$ (4) $Statement I is true but Statement II is false$ 220. $In the Young's double slit experiment, the distance between the slits varies in time as d = d_{0} + a_{0} sin ω t; where d_{0}, ω and a_{0} are constants. The difference between the largest fringe width and the smallest fringe width obtained over time is given as :$ (1) $\frac{2 λ D ( d _{0} )}{( d _{0}^{2} - a _{0}^{2} )}$ (2) $\frac{2 λ D a _{0}}{( d _{0}^{2} - a _{0}^{2} )}$ (3) $\frac{λ D}{d _{0}^{2}} a_{0}$ (4) $\frac{λ D}{d _{0} + a _{0}}$ 221. $Two coherent sources of light interfere. The intensity ratio of two sources is 1 : 4. For this interference pattern if the value of \frac{I _{ma x} + I _{min}}{I _{ma x} - I _{min}} is equal to \frac{2 α + 1}{β + 3}, then \frac{α}{β} will be :$ (1) $1.5$ (2) $2$ (3) $0.5$ (4) $1$ 222. $The phenomenon of polarization shows that light has nature.$ (1) $particle$ (2) $transverse$ (3) $longitudinal$ (4) $dual$ 223. $In Young's double slit experiment, if the source of light changes from orange to blue then:$ (1) $the central bright fringe will become a dark fringe.$ (2) $the distance between consecutive fringes will decrease.$ (3) $the distance between consecutive fringes will increase.$ (4) $the intensity of the minima will increase.$ 224. $In a Young's double slit experiment, three polarizers are kept as shown in the figure. The transmission axes of P_{1} and P_{2} are orthogonal to each other. The polarizer P_{3} covers both the slits with its transmission axis at 45^{\circ} to those of P_{1} and P_{2} . An unpolarized light of wavelength λ and intensity I_{0} is incident on P_{1} and P_{2} . The intensity at a point after P_{3} where the path difference between the light waves from s_{1} and s_{2} is \frac{λ}{3}, is$ (1) $I_{0} 2$ (2) $I_{0} 4$ (3) $I_{0} 3$ (4) $I_{0}$ 225. $If is the intensity of the principal maximum in the single slit diffraction pattern, then what will be the intensity when the slit width is doubled?$ (1) $\frac{I _{0}}{2}$ (2) $I_{0}$ (3) $4 I_{0}$ (4) $2 I_{0}$ 226. $In Young's double slit experiment, a third slit is made in between the double slits. Then$ (1) $fringes of unequal width are formed$ (2) $contrast between bright and dark fringes is reduced$ (3) $intensity of fringes totally disappears$ (4) $only bright light is observed on the screen.$ 227. $Electric field in a plane electromagnetic wave is given by E = 50 sin (500 x - 10 \times 1 0^{10} t) V / m . The velocity of electromagnetic wave in this medium is : (Given C = speed of light in vacuum)$ (1) $\frac{3}{2} C$ (2) $C$ (3) $\frac{2}{3} C$ (4) $\frac{C}{2}$ 228. $In a Young's double slit experiment, two slits are illuminated with a light of wavelength 800 nm. The line joining A_{1} P is perpendicular to A_{1} A_{2} as shown in the figure. If the first minimum is detected at P, the value of slits separation 'a' will be: The distance of screen from slits D = 5 cm$ (1) $0.4 mm$ (2) $0.5 mm$ (3) $0.2 mm$ (4) $0.1 mm$ 229. $Light emerges out of a convex lens when a source of light kept at its focus. The shape of wave front of the light is:$ (1) $both spherical and cylindrical$ (2) $plane$ (3) $spherical$ (4) $cylindrical$ 230. $On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens' principle leads us to conclude that as it travels, the light beam :$ (1) $becomes narrower$ (2) $goes horizontally without any deflection$ (3) $bends downwards$ (4) $bends upwards$ 231. $An unpolarised light beam of intensity 2 I_{0} is passed through a polaroid P and then through another polaroid Q which is oriented in such a way that its passing axis makes an angle of 30° relative to that of P. The intensity of the emergent light is$ (1) $\frac{I _{0}}{4}$ (2) $\frac{I _{0}}{2}$ (3) $\frac{3 I _{0}}{4}$ (4) $\frac{3 I _{0}}{2}$ 232. $The interference pattern is obtained with two coherent light sources of intensity ratio 4:1. And the ratio \frac{I _{ma x} + I _{min}}{I _{ma x} - I _{min}} is \frac{5}{x} . Then, the value of x will be equal to :$ (1) $3$ (2) $4$ (3) $2$ (4) $1$ 233. $Given below are two statements : Statement I : If the Brewster's angle for the light propagating from air to glass is , then Brewster's angle for the light propagating from glass to air is Statement II : The Brewster's angle for the light propagating from glass to air is where is the refractive index of glass. In the light of the above statements, choose the correct answer from the options given below :$ (1) $Both Statements I and Statement II are true.$ (2) $Statement I is true but Statement II is false.$ (3) $Both Statement I and Statement II arc false.$ (4) $Statement I is false but Statement II is true.$ 234. $A cylindrical tube of length 0.2 m and radius R with sugar solution of concentration ' C' produce a rotation of θ in the plane of vibration of a plane polarized light. The same sugar solution is transferred to another tube of length 0.3 m of same radius. The remaining gap is filled by distilled water. Now the optical rotation produced is$ (1) $θ$ (2) $\frac{2 θ}{3}$ (3) $\frac{3 θ}{2}$ (4) $\frac{9 θ}{4}$ 235. $Which of the following phenomena support the wave theory of light?1.Scattering2.Interference3.Diffraction4.Velocity of light in a denser medium is less than the velocity of light in the rarer medium$ (1) $1, 2, 3$ (2) $1, 2, 4$ (3) $2, 3, 4$ (4) $1, 3, 4$ 236. $Consider the following statements in case of Young's double slit experiment. (1) A slit S is necessary if we use an ordinary extended source of light. (2) A slit S is not needed if we use an ordinary but well collimated beam of light. (3) A slit S is not needed if we use a spatially coherent source of light. Which of the above statements are correct?$ (1) $(1), (2) and (3)$ (2) $(1) and (2)$ (3) $(2) and (3)$ (4) $(1) and (3)$ 237. $In single slit experiment, the width of the slit is reduced. Then, the linear width of the principal maxima...$ (1) $increases but becomes less bright$ (2) $decreases but becomes more bright$ (3) $increases but becomes more bright$ (4) $decreases but becomes less bright.$ 238. $In Young's double slit experiment the source is white light. One slit is covered with red filter and the other with blue filter. There shall be$ (1) $alternate red and blue fringes$ (2) $alternate dark and pink fringes$ (3) $alternate dark and yellow fringes$ (4) $no interference.$ 239. $Two luminous point sources separated by a certain distance are at 10 km from an observer. If the aperture of his eye is 2.5 \times 10^{- 3} m and the wavelength of light used is 500 nm, the distance of separation between the point sources just seen to be resolved is$ (1) $12.2 m$ (2) $24.4 m$ (3) $2.44 m$ (4) $1.22 m$ 240. $Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R Assertion A: The beam of electrons shows wave nature and exhibit interference and diffraction. Reason R : Davisson Germer Experimentally verified the wave nature of electrons. In the light of the above statements. Choose the most appropriate answer from the options given below :$ (1) $A is correct but R is not correct$ (2) $A is not correct but R is correct$ (3) $Both A and R are correct but R is Not the correct explanation of A$ (4) $Both A and R are correct and R is the correct explanation of A$