Objective Type Question On Class 12 Physics Chapter 9 Ray Optics and Optical Instruments

1 A concave mirror of focal length f produces an image n times the size of the object. If the image is real then the distance of the object is:

A (n – 1) f

B (n + 1) f

C

D

View Answer

Answer:C

2 The angle of minimum deviation for an equilateral glass prism is 30°. Refractive index of the prism is:

A 1/√3

B √2

C 1

D can’t be determined

View Answer

Answer:√2

3 Light year is the unit of:

A distance

B time

C intensity of light

D None of these

View Answer

Answer:distance

4 A beam of light is incident at 60° to a plane surface. The reflected and refracted rays are perpendicular to each other. What is the R.I. of the surface:

A 1/√3

B √3

C 1/3

D 3

View Answer

Answer:√3

5 A ray of light travelling in air is incident of a glass slab. The ray gets partly reflected and partly refracted. The phase difference between the reflected and the refracted waves is :

A π/2

B π/4

C π

D zero

View Answer

Answer:π

6 Which of-the following is not a property of light?

A It can travel through vacuum

B It has a finite speed

C It requires a material medium for its propagation

D It involve transportation energy

View Answer

Answer:It requires a material medium for its propagation

7 On reflection from a denser medium, a light wave suffers a phase difference of:

A π

B π/2

C π/4

D 2π

View Answer

Answer:π

8 Radio waves from an antenna travel with the velocity of:

A light

B sound

C ultrasonics

D supersonics

View Answer

Answer:light

9 The phase difference between the electric and the magnetic field vectors in electromagnetic waves is

A π/4

B π/2

C π

D zero

View Answer

Answer:zero

10 Refractive index of water and glass are 4/3 and 5/3. A light ray is going to water from glass. Then, its critical angle will be:

A

B

C

D

View Answer

Answer:B

11 A telescope has an objective lens of 10 cm diameter and is situated at a distance of 1 km from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when seen in the light of mean λ = 5000 A is of the order of:

A 5 mm

B 5 cm

C 0.5 m

D 5 m

View Answer

Answer:5 mm

12 Which of the following is not essential for the formation of a pure spectrum?

A parallel beam of light

B narrow beam of light

C screen

D prism in the minimum deviation position

View Answer

Answer:screen

13 A convex lens is dipped in a liquid, whose R.I. is equal to that of R.I. of material of the lens. Then its focal length will:

A become zero

B become infinite

C reduce

D increase

View Answer

Answer:become infinite

14 A certain far-sighted person cannot see objects closer to the eye than 100 cm. The power of the lens which will enable him to read at a distance of 25 cm will be?

A 3D

B 1D

C 4D

D 2D

View Answer

Answer:3D

15 Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is:

A 45 D

B 9 D

C 19 D

D 6 D

View Answer

Answer:9 D

16 A double convex air bubble in water behaves as:

A Convergent lens

B divergent lens

C plane slab

D concave mirror

View Answer

Answer:divergent lens

17 Which produces additional luminiscence in a fluorescent tube?

A infra red rays

B ultraviolet rays

C micro waves

D radio waves

View Answer

Answer:ultraviolet rays

18 The velocity of light in vacuum is 3 × 10¹⁰ cms^-1. The velocity of light in a medium (µ = 1.5) is :

A 2 × 10¹⁰cms^-1

B 4.5 × 10¹⁰cms^-1

C 1.5 × 10¹⁰cms^-1

D None of these

View Answer

Answer:2 × 10¹⁰cms^-1

19 When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is :

A polarized

B of longer λ

C of shorter λ

D of high intensity

View Answer

Answer:of shorter λ

20 The RI. of the material of a prism is √2 and its refracting angle is 30°. One of the refracting surface of the prism is made a mirror. A beam of monochromatic light entering the prism from the other face retraces its path, after reflection from mirror surface. The angle of incidence on prism is:

A 0°

B 30°

C 45°

D 60°

View Answer