Wave Optics · Question 18

Unpolarised light is incident from air on a plane surface of a material of refractive index . At a particular angle of incidence i, it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation?

1. Reflected light is polarised with its electric vector parallel to the plane of incidence
2. Reflected light is polarised with its electric vector perpendicular to the plane of incidence
3. i = -1 ( 1 )
4. i = -1 ( 1 )

In Young's double slit experiment the separation d between the slits is 2 mm, the wavelength of the light used is 5896 A and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.20 . To increase the fringe angular width to 0.21 (with same and D) the separation between the slits needs to be changed to

1. 1.9 mm
2. 1.8 mm
3. 2.1 mm
4. 1.7 mm

The ratio of resolving powers of an optical microscope for two wavelengths 1 = 4000 A and 2 = 6000 A is

1. 9 : 4
2. 3 : 2
3. 16 : 81
4. 8 : 27

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 air. The refractive index of the medium is nearly

1. 1.59
2. 1.69
3. 1.78
4. 1.25

Two polaroids P1 and P2 are placed with their axis perpendicular to each other. Unpolarised light I0 is incident on P1. A third polaroid P3 is kept in between P1 and P2 such that its axis makes an angle 45 with that of P1. The intensity of transmitted light through P2 is

1. I04
2. I08
3. I016
4. I02

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

1. -1 ( 12 )
2. -1 ( 34 )
3. -1 ( 14 )
4. -1 ( 23 )

The intensity at the maximum in a Young's double slit experiment is I0. Distance between two slits is d = 5 , where 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 = 10d?

1. 34I0
2. I02
3. I0
4. I04

The interference pattern is obtained with two coherent light sources of intensity ratio n. In the interference pattern, the ratio Imax - Imin Imax + Imin will be

1. nn + 1
2. 2 nn + 1
3. n(n + 1)2
4. 2 n(n + 1)2

A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm. The aperture is illuminated normally by a parallel beam of wavelength 5 10-5 cm. The distance of the first dark band of the diffraction pattern from the centre of the screen is

1. 0.10 cm
2. 0.25 cm
3. 0.20 cm
4. 0.15 cm

At the first minimum adjacent to the central maximum of a single-slit diffraction pattern, the phase difference between the Huygen's wavelet from the edge of the slit and the wavelet from the midpoint of the slit is

1. radian
2. 8 radian
3. 4 radian
4. 2 radian