Wave Optics

If the screen is moved away from the plane of the slits in a Young's double slit experiment, then the :

1. linear separation of the fringes decreases
2. angular separation of the fringes increases
3. angular separation of the fringes decreases
4. linear separation of the fringes increase

After passing through a polariser a linearly polarised light of intensity I is incident on an analyser making an angle of 30 with that of the polariser. The intensity of light emitted from the analyser will be

1. 2I3
2. I2
3. I3
4. 3I4

Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m is :

1. 1.83 10-7 rad
2. 7.32 10-7 rad
3. 6.00 10-7 rad
4. 3.66 10-7 rad

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