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1.

Young's double-slit experiment is first performed in air and then in a medium other than air. It is found that 8th bright fringe in the medium lies where 5th dark fringe lies in the air. The refractive index of the medium is nearly

(1)1.25

(2) 1.59

(3) 1.69

(4) 1.78

2.

Two polaroids ${P}_{1}and{P}_{2}$ are placed with their axis perpendicular to each other. Unpolarised light ${I}_{o}$ is incident on ${P}_{1}$. A third polaroid ${P}_{3}$ is kept in between ${P}_{1}and{P}_{2}$ such that its axis makes an angle ${45}^{\xb0}$ with that of ${P}_{1}$. The intensity of transmitted light through ${P}_{2}$

(a)$\frac{{I}_{o}}{2}$

(b) $\frac{{I}_{o}}{4}$

(c) $\frac{{I}_{o}}{8}$

(d) $\frac{{I}_{o}}{16}$

3.

The intensity at the maximum in Young's double-slit experiment is ${\mathrm{I}}_{0}$ when the distance between two slits is d=5$\lambda $, where $\lambda $ is the wavelength of light used in the experiment. What will be the intensity in front of one of the slits on the screen placed at a distance D= 10 d?

(a) $\frac{{l}_{0}}{4}$ (b) $\frac{3}{4}{l}_{0}$

(c) $\frac{{l}_{0}}{2}$ (d) ${l}_{0}$

4.

In a diffraction pattern due to a single slit of width a,the first minimum is observed at an angle ${30}^{\circ}$ when light of wavelength 5000 $\dot{A}$ is incident on the slit. The first secondary maximum is observed is an angle of

(a) ${\mathrm{sin}}^{-1}\left(\frac{2}{3}\right)$ (b) ${\mathrm{sin}}^{-1}\left(\frac{1}{2}\right)$

(c) ${\mathrm{sin}}^{-1}\left(\frac{3}{4}\right)$ (d) ${\mathrm{sin}}^{-1}\left(\frac{1}{4}\right)$

5.

In a double-slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double-slit within the central maxima of a single-slit pattern?

1. 0.2 mm

2. 0.1 mm

3. 0.5 mm

4. 0.02 mm

6.

Two slits in Young's experiment have widths in the ratio 1:25. The ratio of intensity at the maxima and minima in the interference pattern I_{max}/I_{min} is

1. 9/4

2. 121/49

3. 49/121

4. 4/9

7.

A beam of light of 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is

1. 1.2cm

2. 1.2mm

3. 2.4cm

4. 2.4mm

8.

In the Young's double-slit experiment, the intensity of light at a point on the screen (where the path difference is λ ) is K where λ being the wavelength of light used. The intensity at a point where the path difference is λ /4 will be

(a) K

(b) K/4

(c) K/2

(d) zero

9.

In a double slit experiment, the distance between the slits is 3 mm and the slits are 2 m away from the screen one due to light with wavelength 480 nm, and the other due to light with wavelength 600 nm. What is the separation on the screen between the fifth order bright fringes of the two interference patterns ?

1. $4\times {10}^{-4}$

2. $9\times {10}^{-4}$

3. $3\times {10}^{-4}$

4. $5\times {10}^{-4}$

10.

Two coherent monochromatic light beams of intensities *I * and 4*I* are superposed. The maximum and minimum possible intensities in the resulting beam are

(1) 5*I* and *I*

(2) 5*I* and 3*I*

(3) 9*I* and *I*

(4) 9*I* and 3*I *

11.

If two waves represented by ${y}_{1}=4\mathrm{sin}\omega t$ and ${y}_{2}=3\mathrm{sin}\left(\omega t+\frac{{\displaystyle \pi}}{{\displaystyle 3}}\right)$ interfere at a point, the amplitude of the resulting wave will be about

(1) 7

(2) 6

(3) 5

(4) 3.5

12.

In Young's experiment, light of wavelength 4000 Å is used to produce bright fringes of width 0.6 *mm*, at a distance of 2 meters. If the whole apparatus is dipped in a liquid of refractive index 1.5, then fringe width will be** **

(1) 0.2 *mm*

(2) 0.3 *mm*

(3) 0.4 *mm*

(4) 1.2 *mm*

13.

In two separate set - ups of the Young's double slit experiment, fringes of equal width are observed when lights of wavelengths in the ratio 1 : 2 are used. If the ratio of the slit separation in the two cases is 2 : 1, the ratio of the distances between the plane of the slits and the screen in the two set - ups is** **

(1) 4 : 1

(2) 1 : 1

(3) 1 : 4

(4) 2 : 1

14.

The slits in a Young's double-slit experiment have equal widths and the source is placed symmetrically relative to the slits. The intensity at the central fringes is *I*_{0}. If one of the slits is closed, the intensity at this point will be

(1) *I*_{0}

(2) *I*_{0 }/ 4

(3) *I*_{0 }/ 2

(4) 4*I*_{0}

15.

A star emitting light of wavelength 5896 Å is moving away from the earth with a speed of 3600 *km/sec*. The wavelength of light observed on earth will

(1) Decrease by 5825.25 Å

(2) Increase by 5966.75 Å

(3) Decrease by 70.75 Å

(4) Increase by 70.75 Å

(*c* = 3 × 10^{8} m/sec is the speed of light)

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