Wave Optics · JEE Main previous year questions

2019 7 questions

1. Q382019 · 12 Apr 2019 · Shift 1

   In a double slit experiment, when a thin film of thickness t having refractive index $\mu$ is introduced in front of one of the slits, the maximum at the centre of the fringe pattern shifts by one fringe width. The value of t is ($\lambda$ is the wavelength of the light used) :

   1. A.$\frac{\lambda }{2(\mu -1)}$
   2. B.$\frac{\lambda }{(2\mu -1)}$
   3. C.$\frac{2\lambda }{(\mu -1)}$
   4. D.$\frac{\lambda }{(\mu -1)}$
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   Answer: D

2. Q412019 · 12 Apr 2019 · Shift 2

   A system of three polarizers $P_1,P_2,P_3$ is set up such that the pass axis of $P_3$ is crossed with respect to that of $P_1$. The pass axis of $P_2$ is inclined at $60^{\circ }$ to the pass axis of $P_3$. When a beam of unpolarized light of intensity $I_0$ is incident on $P_1$, the intensity of light transmitted by the three polarizers is I. The ratio $\left(\frac{I_0}{I}\right)$ equals (nearly) :

   1. A.10.67
   2. B.5.33
   3. C.16.00
   4. D.1.80
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   Answer: A

3. Q432019 · 10 Apr 2019 · Shift 2

   In a Young's double slit experiment, the ratio of the slit's width is 4 : 1. The ratio of the intensity of maxima to minima, close to the central fringe on the screen, will be :

   1. A.25 : 9
   2. B.4 : 1
   3. C.$(\sqrt{3}+1{)}^4:16$
   4. D.9 : 1
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   Answer: D

4. Q482019 · 9 Apr 2019 · Shift 1

   The figure shows a Young's double slit experimental setup. It is observed that when a thin transparent sheet of thickness t and refractive index $\mu$ is put in front of one of the slits, the central maximum gets shifted by a distance equal to n fringe widths. If the wavelength of light used is $\lambda$, t will be : [Figure: slits separated by a, screen at distance D]

   1. A.$\frac{D\lambda }{a(\mu -1)}$
   2. B.$\frac{2nD\lambda }{a(\mu -1)}$
   3. C.$\frac{2D\lambda }{a(\mu -1)}$
   4. D.$\frac{n\lambda }{(\mu -1)}$
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   Answer: D

5. Q322019 · 11 Jan 2019 · Shift 2

   In a double-slit experiment, green light ($5303\text{ A˚}$) falls on a double slit having a separation of $19.44\mu \mathrm{m}$ and a width of $4.05\mu \mathrm{m}$. The number of bright fringes between the first and the second diffraction minima is :

   1. A.04
   2. B.05
   3. C.10
   4. D.09
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   Answer: B

6. Q382019 · 9 Jan 2019 · Shift 1

   Two coherent sources produce waves of different intensities which interfere. After interference, the ratio of the maximum intensity to the minimum intensity is 16. The intensity of the waves are in the ratio :

   1. A.16 : 9
   2. B.25 : 9
   3. C.4 : 1
   4. D.5 : 3
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   Answer: B

7. Q432019 · 9 Jan 2019 · Shift 1
   
   1. A.$\sqrt{\frac{5}{3}}$
   2. B.$\frac{3}{\sqrt{5}}$
   3. C.$\frac{5}{\sqrt{3}}$
   4. D.$\frac{4}{3}$
   Show answer

   Answer: B