Wave Optics

Two wavelengths 1 and 2 are used in Young's double slit experiment. 1=450 nm and 2=650 nm. The minimum order of fringe produced by 2 which overlaps with the fringe produced by 1 is n. The value of n is .

The width of one of the two slits in a Young's double slit experiment is 4 times that of the other slit. The ratio of the maximum to the minimum intensity in the interference pattern is:

1. 1 : 1
2. 4 : 1
3. 16 : 1
4. 9 : 1

A monochromatic light of wavelength 6000 is incident on the single slit of width 0.01 mm. If the diffraction pattern is formed at the focus of the convex lens of focal length 20 cm, the linear width of the central maximum is :

1. 12 mm
2. 24 mm
3. 60 mm
4. 120 mm

A microwave of wavelength 2.0 cm falls normally on a slit of width 4.0 cm. The angular spread of the central maxima of the diffraction pattern obtained on a screen 1.5 m away from the slit, will be :

1. 60
2. 45
3. 15
4. 30

In Young's double slit experiment, monochromatic light of wavelength 5000 Å is used. The slits are 1.0 mm apart and screen is placed at 1.0 m away from slits. The distance from the centre of the screen where intensity becomes half of the maximum intensity for the first time is 10-6 m.

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]