# MCQ Questions Chapter 9 Ray Optics and Optical Instruments Class 12 Physics

Please refer to MCQ Questions Chapter 9 Ray Optics and Optical Instruments Class 12 Physics with answers provided below. These multiple-choice questions have been developed based on the latest NCERT book for class 12 Physics issued for the current academic year. We have provided MCQ Questions for Class 12 Physics for all chapters on our website. Students should learn the objective based questions for Chapter 9 Ray Optics and Optical Instruments in Class 12 Physics provided below to get more marks in exams.

## Chapter 9 Ray Optics and Optical Instruments MCQ Questions

Please refer to the following Chapter 9 Ray Optics and Optical Instruments MCQ Questions Class 12 Physics with solutions for all important topics in the chapter.

MCQ Questions Answers for Chapter 9 Ray Optics and Optical Instruments Class 12 Physics

Question. The optical density of turpentine is higher than that of water while its mass density is lower. Figure shows a layer of turpentine floating over water in a container. For which one of the four rays incident on turpentine in Figure, the path shown is correct?

A) 1
(B) 2
(C) 3
(D) 4

B

Question. There are certain materials developed in laboratories which have a negative refractive index (Figure). A ray incident from air (medium 1) into such a medium (medium 2) shall follow a path given by :

A

Question. Which of the following graphs is the correct angle of incidence vs. angle of deviation graph?

A

Question. The radius of curvature of the curved surface of a plano-convex lens is 20 cm. If the refractive index of the material of the lens be 1.5, it will
(A) act as a convex lens only for the objects that lie on its curved side.
(B) act as a concave lens for the objects that lie on its curved side.
(C) act as a convex lens irrespective of the side on which the object lies.
(D) act as a concave lens irrespective of side on which the object lies.

C

Question. A short pulse of white light is incident from air to a glass slab at normal incidence.
After travelling through the slab, the first colour to emerge is

(A) blue
(B) green
(C) violet
(D) red

D

Question. Radius of curvature of human eye is 0.78 cm. For an object at infinity, image is formed at 3 cm behind the refracting surface. The refractive index of eye is
(A) 1.35
(B) 3
(C) 6.2
(D) 1

A

Question. Magnifying power of a microscope depends on
(A) colour of light.
(B) focal length of objective and colour of light.
(C) focal length of eyepiece and colour of light.
(D) focal length of eyepiece and objective.

D

Question. You are given the following 3 lenses. Two construct an astronomical telescope which one will you used as eyepiece and which one as objective?

(A) L1, L2
(B) L2, L1
(C) L2, L3
(D) L3, L1

B

Question. Magnifying power of a telescope is
(A) 1 / f0 fe
(B) f0 / fe
(C) fe / f0
(D) f0 fe

C

Question. The relationship between angle of incidence i prism of angle A and angle of minimum deviation for a triangular prism is
(A) A + δm = i
(B) A + δm = 2i
(C) A + δm/2 = i
(D) 2A + δm = i

B

Question. If m1 and m2 be the linear magnifications of the objective and eyepiece of a compound microscope, then the magnifying power of the compound microscope is
(A) m1 + m2
(B) m1 – m2
(C) m1 × m2
(D) (m1+m2)/2

C

Question. Reflecting telescope utilises
(A) Convex mirror
(B) Concave mirror
(C) Plane mirror
(D) Prism

B

Question. The magnifying power of a telescope is M. If the focal length of the eyepiece is halved, the magnifying power will become
(A) M/2
(B) 4M
(C) M/4
(D) None of the above

D

Question. In a compound microscope, image produced by objective is ______ and the image produced by eyepiece is ______.
(A) Real, real
(B) Virtual, virtual
(C) Real, virtual
(D) Virtual, real

C

Assertion and Reason Based MCQs

Directions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R).
Mark the correct choice as:
(A) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(C) (A) is true, but (R) is false.
(D) (A) is false, but (R) is true.

Question. Assertion (A): Convex lens behaves like a simple microscope.
Reason (R): For larger magnifying power, the focal length of convex lens should be small.

A

Question. Assertion (A): A diamond of refractive index √6 is immersed in a liquid of refractive index √3 . If light travels from diamond to liquid, total internal reflection will take place when angle of incidence is 30°.
Reason (R): μ = 1/sin C, where μ is the refractive index of diamond with respect to the liquid

D

Question. Assertion (A): A double convex air bubble is formed within a glass slab. The air bubble behaves like a converging lens.
Reason (R): Refractive index of glass is more that the refractive index of air.

D

Question. Assertion (A): Air bubbles shine in water.
Reason (R): Air bubbles shine in water due to refraction of light.

C

Question. Assertion (A): A convex lens of focal length 30 cm can’t be used as a simple microscope in normal setting.
Reason (R): For normal setting, the angular
magnification of simple microscope is M = D/f·

B

Question. Assertion (A): If the objective lens and the eyepiece lens of a microscope are interchanged, it works as a telescope.
Reason (R): Objective lens of telescope require large focal length and eyepiece lens require small focal length.

D

Case-based MCQs

I. Read the following text and answer the following questions on the basis of the same:
Sparking Brilliance of Diamond:
The total internal reflection of the light is used in polishing diamonds to create a sparking brilliance. By polishing the diamond with specific cuts, it is adjusted the most of the light rays approaching the surface are incident with an angle of incidence more than critical angle. Hence, they suffer multiple reflections and ultimately come out of diamond from the top. This gives the diamond a sparking brilliance.

Question. A diamond is immersed in a liquid with a refractive index greater than water. Then the critical angle for total internal reflection will:
(A) depend on the nature of the liquid.
(B) decrease.
(C) remains the same.
(D) increase.

D

Question. The critical angle for a diamond is 24.4°. Then its refractive index is:
(A) 2.42
(B) 0.413
(C) 1
(D) 1.413

A

Question. The basic reason for the extraordinary sparkle of suitably cut diamond is that:
(A) it has low refractive index.
(B) it has high transparency.
(C) it has high refractive index.
(D) it is very hard.

C

Question. Light cannot easily escape a diamond without multiple internal reflections. This is because:
(A) its critical angle with reference to air is too large.
(B) its critical angle with reference to air is too small.
(C) the diamond is transparent.
(D) rays always enter at angle greater than critical angle.

B

Question. The following diagram shows same diamond cut in two different shapes.

The brilliance of diamond in the second diamond will be:
(A) less than the first.
(B) greater than first.
(C) same as first.
(D) will depend on the intensity of light.

A

II. Read the following text and answer the following questions on the basis of the same:
Photometry:
The measurement of light as perceived by human eye is called photometry. Photometry is measurement of a physiological phenomenon, being the stimulus of light as received by the human eye, transmitted by the optic nerves and analysed by the brain. The main physical quantities in photometry are (i) the luminous intensity of the source, (ii) the luminous flux or flow of light from the source and (iii) illuminance of the surface. The SI unit of luminous intensity (I) is candela (cd). The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 Hz and that has a radiant intensity in that direction of 1/683 watt per steradian. If a light source emits one candela of luminous intensity into a solid angle of one steradian, the total luminous flux emitted into that solid angle is one lumen (lm). A standard 100 watt incandescent light bulb emits approximately 1700 lumens.

Question. Light received by human eye is analysed by:
(A) retina
(B) brain
(C) optic nerve
(D) nervous system

B

Question. A standard 100 watt incandescent light bulb emits approximately:
(A) 1700 Lumen
(B) 700 Lumen
(C) 1200 Lumen
(D) 1000 Lumen

A

Question. The SI unit of luminous intensity is:
(A) Dioptre
(C) Candela
(D) Lumen

C

Question. What is photometry?
(A) Measurement of light as perceived by human eye
(B) Measurement of number of photons emerging from a light source
(C) Measurement of electrons emitted by photosensitive surface
(D) Measurement of photosensitivity

A

Question. Unit of luminous flux is:
(A) Candela
(C) Nit
(D) Lumen

D

III. Read the following text and answer the following questions on the basis of the same:
Optical Fibre:
Optical fibre works on the principle of total internal reflection. Light rays can be used to transmit a huge amount of data, but there is a problem here – the light rays travel in straight lines. So unless we have a long straight wire without any bends at all, harnessing this advantage will be very tedious. Instead, the optical cables are designed such that they bend all the light rays’ inwards (using TIR). Light rays travel continuously, bouncing off the optical fibre walls and transmitting end to end data.
It is usually made of plastic or glass.
Modes of transmission: Single-mode fibre is used for long-distance transmission, while multimode fiber is used for shorter distances. The outer cladding of these fibres needs better protection than metal wires. Although light signals do degrade over progressing distances due to absorption and scattering. Then, optical Regenerator system is necessary to boost the signal.
Types of Optical Fibres: The types of optical fibers depend on the refractive index, materials used, and mode of propagation of light. The classification based on the refractive index is as follows:
Step Index Fibres: It consists of a core surrounded by the cladding, which has a single uniform index of refraction.
Graded Index Fibres: The refractive index of the optical fibre decreases as the radial distance from the fibre axis increases.

Question. For long-distance transmission:
(A) single mode fibre is used.
(B) multi-mode fibre is used.
(C) both single mode and multi-mode are used.
(D) any one of single mode or multi-mode may be used.

A

Question. Optical fibre works on the principle of:
(A) scattering of light.
(B) diffraction of light.
(C) total internal reflection of light.
(D) dispersion of light.

C

Question. Light signal through optical fibre may degrade due to:
(A) refraction.
(B) refraction and reflection.
(C) diffraction and scattering.
(D) scattering and absorption.

D

Question. Optical fibre is made of:
(A) copper
(B) semiconductor
(C) plastic or glass
(D) superconductors

C

Question. In graded index optical fibre:
(A) the refractive index of the optical fibre increases as the radial distance from the fibre axis increases.
(B) the refractive index of the optical fibre decreases as the radial distance from the fibre axis increases.
(C) the refractive index of the optical fibre remains same throughout.
(D) inner side of cladding is mirrored to ensure reflection.

B

IV. Read the following text and answer the following questions on the basis of the same:
Negative Refractive Index:
One of the most fundamental phenomena in optics is refraction. When a beam of light crosses the interface between two different materials, its path is altered depending on the difference in the refractive indices of the materials. The greater the difference, the greater the refraction of the beam. For all known naturally occurring materials the refractive index assumes only positive values. But does this have to be the case?
In 1967, Soviet physicist Victor Veselago hypothesized that a material with a negative refractive index could exist without violating any of the laws of physics.
Veselago predicted that this remarkable material would exhibit a wide variety of new optical phenomena. However, until recently no one had found such a material and Veselago’s ideas had remained untested. Recently, meta-material samples are being tested for negative refractive index. But the experiments show significant losses and this could be an intrinsic property of negative index materials.
Snell’s law is satisfied for the materials having a negative refractive index, but the direction of the refracted light ray is ‘mirror-imaged’ about the normal to the surface.

There will be an interesting difference in image formation if a vessel is filled with “negative wate ” having refractive index – 1.33 instead of regular water having refractive index 1.33.
Say, there is a fish in a vessel filled with negative water. The position of the fish is such that the observer cannot see it due to normal refraction since the refracted ray does not reach to his eye.

But due to negative refraction, he will be able to see it since the refracted ray now reaches his eye.

Question. Which of the following is the intrinsic property of negative-index materials?
(A) Significant gain of light energy due to refraction
(B) No loss of light energy due to refraction
(C) Significant loss of light energy due to refraction
(D) Loss of energy due to refraction in intermittent

C

Question. Is Snell’s law applicable for negative refraction ?
(A) Yes
(B) No
(C) Unpredictable
(D) Yes, only for normal incidence

A

Question. A ray in incident on normal glass and “negative glass” at an angle 60°. If the magnitude of angle of refraction in normal glass is 45° then, what will be the magnitude of angle of refraction in the “negative glass”?
(A) Less than 45°
(B) More than 45°
(C) 45°
(D) Unpredictable

C

Question. Who hypothesized that a material may have negative refractive index ?
(A) Joseph Von Fraunhofer
(B) Augustin-Jean Fresnel
(C) Thomas Moore
(D) Victor Veselago
Ans. Option (D) is correct.

D

Question. When the angle of incidence will be equal to angle of refraction for material having negative refraction index?
(A) When angle of incidence = 90°
(B) When angle of incidence = 0°
(C) It will vary from material to material
(D) It is never possible

B

Assertion-Reason Questions

In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct answer out of the following choices.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

Question. Assertion (A): The speed of light in glass depends on colour of light.
Reason (R): The speed of light in glass vg = c/ng, the refractive index (ng) of glass is different for different colours.

A

Question. Assertion (A): The resolving power of a telescope is more, if the diameter of the objective lens is more.
Reason (R): Objective lens of large diameter collects more light.

B

Question. Assertion (A): If a convex lens is kept in water, its convergence power decreases.
Reason (R): The refractive index of convex lens relative to water is less than that relative to air.

A

Question. Assertion (A): Light travels faster in glass than in air.
Reason (R): Glass medium is rarer than air.

D

Question. Assertion (A): Magnifying glass is formed of shorter focal length.
Reason (R): It is easier to form lenses of small focal length.

C

Question. Assertion (A): For observing traffic at back, the driver mirror is convex mirror.
Reason (R): A convex mirror has much larger field of view than a plane mirror.

A

Question. Assertion (A): Diamond glitters brilliantly.
Reason (R): Diamond reflects sunlight strongly.

C

Question. Assertion (A): In astronomical telescope, the objective lens is of large aperture.
Reason (R): Larger is the aperture, smaller is the magnifying power.

C

Question. Assertion (A): In compound microscope, the objective lens is taken of small focal length.
Reason (R): This increases the magnifying power of microscope.