Wave Optics · JEE Main previous year questions

2020 8 questions

1. Q412020 · 3 Sept 2020 · Shift 1

   In a Young's double slit experiment, light of 500 nm is used to produce an interference pattern. When the distance between the slits is 0.05 mm, the angular width (in degree) of the fringes formed on the distance screen is close to

   1. A.$0.17^{\circ }$
   2. B.$1.7^{\circ }$
   3. C.$0.57^{\circ }$
   4. D.$0.07^{\circ }$
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   Answer: C

2. Q282020 · 2 Sept 2020 · Shift 1

   Interference fringes are observed on a screen by illuminating two thin slits 1 mm apart with a light source ($\lambda =632.8\text{ nm}$). The distance between the screen and the slits is 100 cm. If a bright fringe is observed on a screen at a distance of 1.27 mm from the central bright fringe, then the path difference between the waves, which are reaching this point from the slits is close is

   1. A.$1.27\mu \mathrm{m}$
   2. B.$2.05\mu \mathrm{m}$
   3. C.2.87 nm
   4. D.2 nm
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   Answer: A

3. Q272020 · 2 Sept 2020 · Shift 2

   In a Young’s double slit experiment, 16 fringes are observed in a certain segment of the screen when light of a wavelength 700 nm is used. If the wavelength of light is changed to 400 nm, the number of fringes observed in the same segment of the screen would be

   1. A.28
   2. B.24
   3. C.30
   4. D.18
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   Answer: A

4. Q492020 · 9 Jan 2020 · Shift 2· Numerical answer

   In a Young's double slit experiment 15 fringes are observed on a small portion of the screen when light of wavelength 500 nm is used. Ten fringes are observed on the same section of the screen when another light source of wavelength $\lambda$ is used. Then the value of $\lambda$ is (in nm) _______.

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   Answer: 750

5. Q272020 · 8 Jan 2020 · Shift 2

   In a double slit experiment, at a certain point on the screen the path difference between the two interfering waves is $\frac{1}{8}\text{th}$ of a wavelength. The ratio of the intensity of light at that point to that at the centre of a bright fringe is :

   1. A.0.853
   2. B.0.568
   3. C.0.672
   4. D.0.760
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   Answer: A

6. Q282020 · 7 Jan 2020 · Shift 1

   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. A.$71.6^{\circ }$
   2. B.$90^{\circ }$
   3. C.$18.4^{\circ }$
   4. D.$45^{\circ }$
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   Answer: C

7. Q432020 · 7 Jan 2020 · Shift 1

   Visible light of wavelength $6000\times 10^{-8}\mathrm{cm}$ falls normally on a single slit and produces a diffraction pattern. It is found that the second diffraction minimum is at $60^{\circ }$ from the central maximum. If the first minimum is produced at ${\theta }_1$, then ${\theta }_1$, is close to :

   1. A.$45^{\circ }$
   2. B.$30^{\circ }$
   3. C.$25^{\circ }$
   4. D.$20^{\circ }$
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   Answer: C

8. Q362020 · 7 Jan 2020 · Shift 2

   In a Young's double slit experiment, the separation between the slits is 0.15 mm. in the experiment, a source of light of wavelengh 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. A.4.9 mm
   2. B.5.9 mm
   3. C.6.9 mm
   4. D.3.9 mm
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   Answer: B