Wave Optics

Two waves of intensity ratio 1:9 cross each other at a point. The resultant intensities at that point, when (a) Waves are incoherent is I1 (b) Waves are coherent is I2 and differ in phase by 60 . If I1I2= 10x then x= .

When unpolarized light is incident at an angle of 60 on a transparent medium from air, the reflected ray is completely polarized. The angle of refraction in the medium is:

1. 60
2. 90
3. 30
4. 45

The diffraction pattern of a light of wavelength 400 nm diffracting from a slit of width 0.2 mm is focused on the focal plane of a convex lens of focal length 100 cm. The width of the 1st secondary maxima will be :

1. 2 mm
2. 0.2 mm
3. 0.02 mm
4. 2 cm

A beam of unpolarised light of intensity I0 is passed through a polaroid A and then through another polaroid B which is oriented so that its principal plane makes an angle of 45 relative to that of A. The intensity of emergent light is:

1. I0/2
2. I0/8
3. I0/4
4. I0

In a double slit experiment shown in figure, when light of wavelength 400 nm is used, dark fringe is observed at P. If D=0.2 m, the minimum distance between the slits S1 and S2 is mm. [figure]

In Young's double slit experiment, light from two identical sources are superimposing on a screen. The path difference between the two lights reaching at a point on the screen is 7 /4. The ratio of intensity of fringe at this point with respect to the maximum intensity of the fringe is :

1. 12
2. 34
3. 13
4. 14

In a single slit diffraction pattern, a light of wavelength 6000 A is used. The distance between the first and third minima in the diffraction pattern is found to be 3 mm when the screen is placed 50 cm away from slits. The width of the slit is 10-4 m.

When a polaroid sheet is rotated between two crossed polaroids then the transmitted light intensity will be maximum for a rotation of :

1. 90
2. 30
3. 45
4. 60

A parallel beam of monochromatic light of wavelength 5000 Å is incident normally on a single narrow slit of width 0.001 mm. The light is focused by convex lens on screen, placed on its focal plane. The first minima will be formed for the angle of diffraction of (degree).