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

Questions
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 Class 12 Physics Chapter 9 Ray Optics and Optical Instruments
D Class 12 Physics Chapter 9 Ray Optics and Optical Instruments

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

Answer:√2
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3 Light year is the unit of:
A distance
B time
C intensity of light
D None of these

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

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

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

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

Answer:π
8 Radio waves from an antenna travel with the velocity of:
A light
B sound
C ultrasonics
D supersonics

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

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 Class 12 Physics Chapter 9 Ray Optics and Optical Instruments
B Class 12 Physics Chapter 9 Ray Optics and Optical Instruments
C Class 12 Physics Chapter 9 Ray Optics and Optical Instruments
D Class 12 Physics Chapter 9 Ray Optics and Optical Instruments

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

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

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

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

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

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

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

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

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

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°

Answer:45°

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