Wave Optics PYQs Set 5 (PDF)

Set 5 of 9 · Questions 121-150 of 243

In the print window choose “Save as PDF”. The file prints without a web address or date line.

Mere Teacher · Previous Year Questions NEET Physics · Wave Optics · Set 5 (Q121-150)
Scan or visit mereteacher.com for free PYQ practice, timed CBT tests, step-by-step solutions and BroBot AI. Answers and solutions are free with a sign-up.
121. $The critical angle of a certain medium is sin^{- 1} (\frac{3}{5}) The polarizing angle of the medium is$ (1) $sin^{- 1} (\frac{4}{5})$ (2) $tan^{- 1} (\frac{5}{3})$ (3) $tan^{- 1} (\frac{3}{4})$ (4) $tan^{- 1} (\frac{4}{5})$ 122. $An unpolarised beam of intensity I_{0} is incident on a pair of nicols making an angle of 60^{\circ} with each other. The intensity of light emerging from the pair is$ (1) $I_{0}$ (2) $I_{0} /2$ (3) $I_{0} /4$ (4) $I_{0} /8 .$ 123. $In a system of two crossed polarisers, it is found that the intensity of light from the second polariser is half from that of first polariser. The angle between their pass axes is$ (1) $30^{\circ}$ (2) $0^{\circ}$ (3) $45^{\circ}$ (4) $60^{\circ}$ 124. $In Young's double slit experiment, point A on the screen has a path difference of λ and point B on the screen has a path difference of \frac{λ}{4} . What is the ratio of the intensities at point A to B ?$ (1) $1 : 1$ (2) $2 : 1$ (3) $1 : 2$ (4) $4 : 1$ 125. $In a Young's double slit experiment with slit separation 0.1 mm one observes a bright fringe at angle \frac{1}{40} by using light of wavelength λ_{1} When the light of wavelength λ_{2} is used a bright fringe is seen at the same angle in the same set up. Given that λ_{1} and λ_{2} are in visible range 380 nm to 740 nm, their values are:$ (1) $625 nm, 500 nm$ (2) $380 nm, 525 nm$ (3) $380 nm, 500 nm$ (4) $400 nm, 500 nm$ 126. $When a polaroid sheet is rotated between two crossed polaroids then the transmitted light intensity will be maximum for a rotation of:$ (1) $60^{\circ}$ (2) $30^{\circ}$ (3) $90^{\circ}$ (4) $45^{\circ}$ 127. $A single slit Fraunh offer diffraction pattern is formed with white light. For what wavelength of light, the third secondary maximum in the diffraction pattern coincides with the second secondary maximum in the pattern for red light of wavelength ?$ (1) $4400Å$ (2) $4100Å$ (3) $4642.8Å$ (4) $9100Å$ 128. $Through a narrow slit of width , diffraction pattern is formed on a screen kept at a distance from the slit. The wavelength of the light used is and falls normal to the slit and screen. Then, the distance between the two minima on either side of the central maximum is$ (1) $12.6 mm$ (2) $1.27 mm$ (3) $2.532 mm$ (4) $25.3 mm$ 129. $An unpolarized light of intensity I is passed through two polaroids kept one after the other with their planes parallel to each other. The intensity of light emerging from second polaroid is \frac{I}{4} . The angle between the pass axes of the polaroid is$ (1) $45^{\circ}$ (2) $0^{\circ}$ (3) $60^{\circ}$ (4) $30^{\circ}$ 130. $Resolving power of telescope increases when$ (1) $wavelength of light decreases$ (2) $wavelength of light increases$ (3) $focal length of eye piece increases$ (4) $foeal length of eye piece decreases$ 131. $A monochromatic light of wavelength is incident on the single slit of width . If the diffraction pattern is formed at the focus of the convex lens of focal length , the linear width of the central maximum is :$ (1) $60 mm$ (2) $24 mm$ (3) $120 mm$ (4) $12 mm$ 132. $In a single slit diffraction, the slit is illuminated with light of wavelength . If the slit were illuminated by a light of wavelength the angular width of the central maximum decreases by . Then is$ (1) $6000Å$ (2) $4200Å$ (3) $3000Å$ (4) $1800Å$ 133. $In a Fraunhofer diffaction experiment at a single slit using a light of wavelength 400 nm, the first minimum is formed at an angle of 30^{\circ} . The direction θ of the first secondary maximum is given by$ (1) $sin^{- 1} (1/4)$ (2) $tan^{- 1} (2/3)$ (3) $sin^{- 1} (2/3)$ (4) $sin^{- 1} (3/4)$ 134. $Light consisting of a plane waves of wavelength, λ_{1} = 8 \times 10^{- 5} cm and λ_{2} = 6 \times 10^{- 5} cm generates an interference pattern in Young's double slit experiment. If n_{1} denotes the n_{1} th dark fringe due to light of wavelength λ_{1} which coincides with n_{2} th bright fringe due to light of wavelength λ_{2}, then$ (1) $n_{1} = 3, n_{2} = 1$ (2) $n_{1} = 4, n_{2} = 5$ (3) $n_{1} = 1, n_{2} = 2$ (4) $n_{1} = 3, n_{2} = 2$ 135. $Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In Young's double slit experiment, the fringes produced by red light are closer as compared to those produced by blue light. Reason (R): The fringe width is directly proportional to the wavelength of light. choose the correct answer from the options given below :$ (1) $Both (A) and (R) are true but (R) is NOT the correct explanation of (A)$ (2) $(A) is true but (R) is false$ (3) $Both (A) and (R) are true and (R) is the correctexplanation of (A)$ (4) $(A) is false but (R) is true$ 136. $The sources of light of wavelength 2500Å and 3500 A are used in Youngs double slit experiment simultaneously: Which orders of fringes of two wavelength patterns coincide?$ (1) $3^{nd} order of 1^{st} and 5^{th} order of 2^{nd}$ (2) $7^{th} order of 1^{st} and 5^{th} order of 2^{nd}$ (3) $5^{th} order of 1^{st} and 3^{rd} order of 2^{nd}$ (4) $5^{th} order of 1^{st} and 7^{th} order of 2^{nd}$ 137. $In Fraunhofer diffraction pattern, slit width is and screen is at away from the lens. If wavelength of light used is then the distance between the first minimum on either side the central maximum is ( is small and measured in radian)$ (1) $10^{- 1} m$ (2) $10^{- 2} m$ (3) $2\times 1 0^{- 2} m$ (4) $2\times 1 0^{- 1} m$ 138. $In a Young's double slit experiment, the source is white light. One of the slits is covered by red filter and another by a green filter. In this case:$ (1) $there shall be alternate interference fringes of red and green.$ (2) $there shall be an interference pattern for red distinct from that for green. there shall be an interference pattern,$ (3) $where each fringe's pattern center is green and outer edges is red.$ (4) $there shall be no interference fringes.$ 139. $Two plane polarized light waves combine at a certain point whose electric field components are E_{1} = E_{0} Sinωt E_{2} = E_{0} Sin (ωt + \frac{π}{3}) Find the amplitude of the resultant wave.$ (1) $1.7 E_{0}$ (2) $E_{0}$ (3) $0.9 E_{0}$ (4) $3.4 E_{0}$ 140. $Two slits separated by 0.5 mm are illuminated by light of wavelength 500 nm . The screen is at a distance of 120 cm from the slits. The phase difference between the interfering waves at a point 3 mm on the screen from the central bright fringe is\dots\dots\dots\dots.$ (1) $5 π$ (2) $π$ (3) $3 π$ (4) $7 π$ 141. $The diffraction pattern of a light of wavelength diffracting from a slit of width is focused on the focal plane of a convex lens of focal length . The width of the secondary maxima will be :$ (1) $2 mm$ (2) $2 cm$ (3) $0.02 mm$ (4) $0.2 mm$ 142. $In a Young's double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is :$ (1) $15.6 mm$ (2) $1.56 mm$ (3) $7.8 mm$ (4) $9.75 mm$ 143. $To observe diffraction, the size of the obstacle$ (1) $should be λ /2, where λ is the wavelength$ (2) $should be of the order of wavelength$ (3) $has no relation to wavelength$ (4) $should be much larger than the wavelength.$ 144. $Light of wavelength is incident on a single slit of width and the distance between slit and screen is . In diffraction pattern, if slit width is equal to the width of the central maximum, then is equal to$ (1) $a /2 λ$ (2) $a^{2} /2 λ$ (3) $a / λ$ (4) $a^{2} / λ$ 145. $When the angle of incidence is 60^{\circ} on the surface of a glass slab, it is found that the reflected ray is completely polarised. The velocity of light in glass is$ (1) $2 \times 10^{8} ms^{- 1}$ (2) $3 \times 10^{8} ms^{- 1}$ (3) $2 \times 10^{8} m s^{- 1}$ (4) $3 \times 10^{8} m s^{- 1}$ 146. $Diameter of the objective lens of a telescope is 250 cm . For light of wavelength 600 nm . Coming from a distant object, the limit of resolution of the telescope is close to:$ (1) $1.5 \times 10^{- 7} rad$ (2) $2.0 \times 10^{- 7} rad$ (3) $3.0 \times 10^{- 7} rad$ (4) $4.5 \times 10^{- 7} rad$ 147. $Two coherent plane waves of identical frequency and intensity (I) interfere at a point, where they differ in phase by 60^{\circ} . What is the resulting intensity?$ (1) $I$ (2) $2 I$ (3) $3 I$ (4) $41$ 148. $Two coherent monochromatic light beams of intensities ' 4 r and ' 9 r are superimposed. The maximum and minimum possible intensities in the resulting beam are$ (1) $3I and 2 I$ (2) $9 I and 5 I$ (3) $16 I and 3I$ (4) $25 I and I$ 149. $Visible light of wavelength falls normally on single slit and produces a diffraction pattern. It is found that the second diffraction minimum is at from the central maximum. If the first minimum is produced at , then is close to :$ (1) $25^{\circ}$ (2) $30^{\circ}$ (3) $20^{\circ}$ (4) $45^{\circ}$ 150. $A polarizer - analyser set is adjusted such that the intensity of light coming out of the analyser is just 10 % of the original intensity. Assuming that the polarizer-analyser set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero is:$ (1) $45^{\circ}$ (2) $90^{\circ}$ (3) $71.6^{\circ}$ (4) $18.4^{\circ}$