Wave Optics

In Young's double slit experiment, using monochromatic light of wavelength λ, the intensity of light at a point on the screen where the path difference is λ, is K units. The intensity of light at a point where the path difference is 3 will be :

1. K
2. 2 K
3. K2
4. K4

In interference and diffraction, the light energy is redistributed. If it reduces in one region, producing a dark fringe, it increases in another region, producing a bright fringe. Choose the correct answer from the options given below :

1. A is false, but B is true
2. A is true, but B is false
3. A is true and B is also true
4. Both A and B are false

The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at 22.5 from the polarization axis of one of the polaroids, is (I0 is the intensity of polarised light after passing through the first polaroid):

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

An unpolarized light beam travelling in air is incident on a medium of refractive index 1.73 at Brewster's angle. Then

1. Both reflected and transmitted light are perfectly polarized with angles of reflection and refraction close to 60 and 30 , respectively
2. Transmitted light is completely polarized with angle of refraction close to 30
3. Reflected light is completely polarized and the angle of reflection is close to 60
4. Reflected light is partially polarized and the angle of reflection is close to 30

If the monochromatic source in Young's double slit experiment is replaced by white light, then

1. Interference pattern will disappear
2. There will be a central dark fringe surrounded by a few coloured fringes
3. There will be a central bright white fringe surrounded by a few coloured fringes
4. All bright fringes will be of equal width

An unpolarised light beam strikes a glass surface at Brewster's angle. Then

1. The reflected light will be partially polarised.
2. The refracted light will be completely polarised.
3. Both the reflected and refracted light will be completely polarised.
4. The reflected light will be completely polarised but the refracted light will be partially polarised.

Two slits in Young's double slit experiment are 1.5 mm apart and the screen is placed at a distance of 1 m from the slits. If the wavelength of light used is 600 10-9 m then the fringe separation is

1. 4 10-5 m
2. 9 10-8 m
3. 4 10-7 m
4. 4 10-4 m

Interference pattern can be observed due to superposition of the following waves: Choose the correct answer from the options given below.

1. B and C
2. B and D
3. A and C
4. A and B

A beam of unpolarized light of intensity I0 is passed through a polaroid A, then through another polaroid B, oriented at 60 and finally through another polaroid C, oriented at 45 relative to B as shown. The intensity of emergent light is: [figure]

1. I016
2. I04
3. I02
4. I032

For Young's double slit experiment, two statements are given below : In the light of the above statements, choose the correct answer from the options given below :

1. Both Statement I and Statement II are false
2. Statement I is true but Statement II is false
3. Statement I is false but Statement II is true
4. Both Statement I and Statement II are true

In a Young's double slit experiment, a student observes 8 fringes in a certain segment of screen when a monochromatic light of 600 nm wavelength is used. If the wavelength of light is changed to 400 nm, then the number of fringes he would observe in the same region of the screen is

1. 6
2. 8
3. 9
4. 12

A light ray falls on a glass surface of refractive index 3, at an angle 60 . The angle between the refracted and reflected rays would be

1. 30
2. 60
3. 90
4. 120

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

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

Two slits in Young's experiment have widths in the ratio 1 : 25. The ratio of intensity at the maxima and minima in the interference pattern, I I is

1. 49121
2. 49
3. 94
4. 12149

For a parallel beam of monochromatic light of wavelength ' ', diffraction is produced by a single slit whose width 'a' is of the order of the wavelength of the light. If 'D' is the distance of the screen from the slit, the width of the central maxima will be

1. Da
2. 2Da
3. 2D a
4. D a