Wave Optics · JEE Main previous year questions

2021 7 questions

1. Q522021 · 1 Sept 2021 · Shift 2· Numerical answer

   The width of one of the two slits in a Young's double slit experiment is three times the other slit. If the amplitude of the light coming from a slit is proportional to the slit-width, the ratio of minimum to maximum intensity in the interference pattern is x : 4 where x is ____________.

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   Answer: 1

2. Q422021 · 25 Jul 2021 · Shift 1

   In the Young's double slit experiment, the distance between the slits varies in time as $d(t)=d_0+a_0\sin \omega t$; where $d_0$, $\omega$ and $a_0$ are constants. The difference between the largest fringe width and the smallest fringe width obtained over time is given as :

   1. A.$\frac{2\lambda D(d_0)}{(d_0^2-a_0^2)}$
   2. B.$\frac{2\lambda D{a}_0}{(d_0^2-a_0^2)}$
   3. C.$\frac{\lambda D}{d_0^2}{a}_0$
   4. D.$\frac{\lambda D}{d_0+a_0}$
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   Answer: B

3. Q442021 · 25 Jul 2021 · Shift 1

   A linearly polarized electromagnetic wave in vacuum $$E=3.1\cos \left[(1.8)z-(5.4\times 10^6)t\right]\hat{i}N/C$$ is incident normally on a perfectly reflecting wall at z = a. Choose the correct option

   1. A.The wavelength is 5.4 m
   2. B.The frequency of electromagnetic wave is $54\times 10^4$ Hz.
   3. C.The transmitted wave will be $3.1\cos \left[(1.8)z-(5.4\times 10^6)t\right]\hat{i}N/C$
   4. D.The reflected wave will be $3.1\cos \left[(1.8)z+(5.4\times 10^6)t\right]\hat{i}N/C$
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   Answer: D

4. Q372021 · 18 Mar 2021 · Shift 1

   In Young's double slit arrangement, slits are separated by a gap of 0.5 mm, and the screen is placed at a distance of 0.5 m from them. The distance between the first and the third bright fringe formed when the slits are illuminated by a monochromatic light of $5890\text{ A˚}$ is :-

   1. A.$1178\times 10^{-9}\text{ m}$
   2. B.$1178\times 10^{-6}\text{ m}$
   3. C.$1178\times 10^{-12}\text{ m}$
   4. D.$5890\times 10^{-7}\text{ m}$
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   Answer: B

5. Q522021 · 16 Mar 2021 · Shift 1· Numerical answer

   A fringe width of 6 mm was produced for two slits separated by 1 mm apart. The screen is placed 10 m away. The wavelength of light used is 'x' nm. The value of 'x' to the nearest integer is ____________.

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   Answer: 600

6. Q372021 · 26 Feb 2021 · Shift 1

   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. A.0.50 mm
   2. B.0.25 mm
   3. C.1 mm
   4. D.0.75 mm
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   Answer: B

7. Q352021 · 25 Feb 2021 · Shift 2

   Consider the diffraction pattern obtained from the sunlight incident on a pinhole of diameter $0.1\mu \mathrm{m}$. If the diameter of the pinhole is slightly increased, it will affect the diffraction pattern such that:

   1. A.its size increases, but intensity decreases
   2. B.its size increases, and intensity increases
   3. C.its size decreases, but intensity increases
   4. D.its sizes decreases, and intensity decreases
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   Answer: C