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NEET Physics : Wave Optics

Multiple Choice Questions

121.

In the Young's double slit experiment, the central maxima is observed to be I_0. If one of the slits is covered, then the intensity at the central maxima will become

$\frac{I_{0}}{2}$
$\frac{I_{0}}{\sqrt{2}}$
$\frac{I_{0}}{4}$
$I_{0}$

122.

A fish at a depth of 12 cm in water is viewed by an observer on the bank of a lake. To what height the image of the fish is raised ?

9 cm
12 cm
3.8 cm
3 cm

123.

In Young's double slit experiment the two slits are d distance apart. Interference pattern is observed on a screen at a distance D from the slits. A dark fringe is observed on the screen directly opposite to one of the slits. The wavelength of light is

$\frac{D^{2}}{2 d}$
$\frac{d^{2}}{2 D}$
$\frac{D^{2}}{d}$
$\frac{d^{2}}{D}$

124.

The light beams of intensities in the ratio of 9 : 1 are allowed to interfere. What will be the ratio of the intensities of maxima and minima ?

3 : 1
4 : 1
25 : 9
81 : 1

125.

Two identical light waves, propagating in the same direction, have a phase difference 6. After they superpose the intensity of the resulting wave will be proportional to

$\cos δ$
$\cos (\frac{δ}{2})$
$\cos^{2} (\frac{δ}{2})$
$\cos^{2} δ$

126.

Two coherent monochromatic beams of intensities I and 41 respectively are superposed. The maximum and minimum intensities in the resulting pattern are

5I and 3I
9I and 3I
4I and I
9I and I

127.

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance froni the slit. If the speed of the electrons is increased, then which of the following statements is correct ?

Diffraction pattern is not observed on the screen in the case of electrons
The angular width of the central maximum of the diffraction pattern will increase
The angular width of the central maximum will decrease
The angular width of the central maximum will be unaffected

128.

A ray of light is incident at 50° on the middle of one of the two mirrors arranged at an angle of 60° between them. The ray then touches the second mirror, gets reflected back to the first mirror, making an angle of incidence

50°
60°
70°
80°

129.

In Young's double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ₁ = 12000 $\overset{\circ}{A}$ and λ₂ = 10000 $\overset{\circ}{A}$ . At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ?

8 mm
6 mm
4 mm
3 mm

130.

In Young's double slit experiment, the fringe width is β. If the entire arrangement is placed in a liquid of refractive index n, the fringe width becomes

nβ
$\frac{β}{n + 1}$
$\frac{β}{n - 1}$
$\frac{β}{n}$

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NEET Physics : Wave Optics

Multiple Choice Questions