Ray Optics and Optical Instruments · Question 56

A ray of light is incident on a 60 prism at the minimum deviation position. The angle of refraction at the first face (i.e., incident face) of the prism is

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

A ray of light travelling in a transparent medium of refractive index , falls on a surface separating the medium from air at an angle of incidence of 45 . For which of the following value of the ray can undergo total internal reflection?

1. = 1.33
2. = 1.40
3. = 1.50
4. = 1.25

A lens having focal length f and aperture of diameter d forms an image of intensity I. Aperture of diameter d2 in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively

1. f and I4
2. 3f4 and I2
3. f and 3I4
4. f2 and I2

Two thin lenses of focal lengths f1 and f2 are in contact and coaxial. The power of the combination is

1. f1 + f22
2. f1 + f2f1 f2
3. f1f2
4. f2f1

A boy is trying to start a fire by focusing sunlight on a piece of paper using an equiconvex lens of focal length 10 cm. The diameter of the sun is 1.39 109 m and its mean distance from the earth is 1.5 1011 m. What is the diameter of the sun's image on the paper ?

1. 6.5 10-5 m
2. 12.4 10-4 m
3. 9.2 10-4 m
4. 6.5 10-4 m

A small coin is resting on the bottom of a beaker filled with liquid. A ray of light from the coin travels up to the surface of the liquid and moves along its surface. How fast is the light travelling in the liquid? [figure]

1. 2.4 108 m/s
2. 3.0 108 m/s
3. 1.2 108 m/s
4. 1.8 108 m/s

The frequency of a light wave in a material is 2 1014 Hz and wavelength is 5000 A. The refractive index of material will be

1. 1.50
2. 3.00
3. 1.33
4. 1.40

A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again ?

1. 2 cm upward
2. 1 cm upward
3. 4.5 cm downward
4. 1 cm downward

A convex lens and a concave lens, each having same focal length of 25 cm, are put in contact to form a combination of lenses. The power in diopters of the combination is

1. zero
2. 25
3. 50
4. infinite.

The refractive index of the material of a prism is 2 and its refracting angle is 30 . One of the refracting surfaces of the prism is made a mirror inwards. A beam of monochromatic light entering the prism from the other face will retrace its path after reflection from the mirrored surface if its angle of incidence on the prism is

1. 45
2. 60
3. 0
4. 30