Wave Optics

In Young's double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes :

1. half
2. four times
3. one-fourth
4. double

The Brewster's angle ib for an interface should be :

1. 30 < ib < 45
2. 45 < ib < 90
3. ib = 90
4. 0 < ib < 30

In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be 0.2°. What will be the angular width of the first minima, ( water = 4/3) if the entire experimental apparatus is immersed in water?

1. 0.15°
2. 0.05°
3. 0.1°
4. 0.266°

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