# CBSE Class 12 Physics Ray Optics and Optical Instruments MCQs

## MCQ for Class 12 Physics Ray Optics and Optical Instruments

Class 12 Physics students should refer to the following multiple-choice questions with answers for Ray Optics and Optical Instruments in standard 12. These MCQ questions with answers for Grade 12 Physics will come in exams and help you to score good marks

### Ray Optics and Optical Instruments MCQ Questions Class 12 Physics with Answers

Question : The light reflected by a plane mirror may form a real image

(a) if the rays incident on the mirror are diverging
(b) if the rays incident on the mirror are converging
(c) if the object is placed very close to the mirror
(d) under no circumstances

Question : In image formation from spherical mirrors, only paraxial rays are considered because they

(a) are easy to handle geometrically
(b) contain most of the intensity of the incident light
(c) form nearly a point image of a point source
(d) show minimum dispersion effect

Question : For reflection through spherical surfaces, the normal at the point of incidence is

(a) perpendicular to the principle axis and passes through the centre of curvature
(b) perpendicular to the focal plane and passes through the pole.
(c) perpendicular to the tangent plane at pole and passes through the focus.
(d) perpendicular to the tangent plane at the point of incidence and passes through the centre of curvature.

Question : A person is six feet tall. How tall must a plane mirror be if he is able to see his entire length?

(a) 3 ft
(b) 4.5 ft
(c) 7.5 ft
(d) 6 ft

Question : An object is placed 40 cm from a concave mirror of focal length 20 cm. The image formed is

(a) real, inverted and same in size
(b) real, inverted and smaller
(c) virtual, erect and larger
(d) virtual, erect and smaller

Question : Which of the following is incorrect statement?

(a) the magnification produced by a convex mirror is always less than one
(b) a virtual, erect, same-sized image can be obtained using a plane mirror
(c) a virtual, erect, magnifield image can be formed using a concave mirror
(d) a real, inverted, same-sized image can be formed using a convex mirror.

Question : Total internal reflection can take place only if

(a) light goes from optically rarer medium (smaller refractive index) to optically denser medium
(b) light goes from optically denser medium to rarer medium
(c) the refractive indices of the two media are close to different
(d) the refractive indices of the two media are widely different

Question : When the angle of incidence of a light ray is greater than the critical angle it gets

(a) critically refracted
(b) totally reflected
(c) total internally reflected
(d) totally refracted

Question : Critical angle of light passing from glass to water is minimum for

(a) red colour
(b) green colour
(c) yellow colour
(d) violet colour

Question : A glass slab of thickness 4 cm contains the same number of waves as 5 cm of water when both are traversed by the same monochromatic light. If the refractive index of water is 4/3, what is that of glass?

(a) 5/3
(b) 5/4
(c) 16/15
(d) 1.5

Question : A point object is placed at the centre of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is

(a) 2 cm
(b) 4 cm
(c) 6 cm
(d) 12 cm

Question : A planoconvex lens of focal length 16 cm, is to be made of glass of refractive index 1.5. The radius of curvature of the curved surface should be

(a) 8 cm
(b) 12 cm
(c) 16 cm
(d) 24 cm

Question : Electromagnetic radiation belonging to _________ region of spectrum is called light.
(a) 100 nm to 400 nm
(b) 400 nm to 750 nm
(c) 750 nm to 10 nm
(d) 1000 nm to 1400 nm

Question : The turning back of light into the same medium after incident on a boundary separating two media is called
(a) reflection of light
(b) refraction of light
(c) dispersion of light
(d) interference of light

Question : A point source of light is placed in front of a plane mirror. Then
(a) all the reflected rays meet at a point when produced backward
(b) only the reflected rays close to the normal meet at a point when produced backward.
(c) only the reflected rays making a small angle with the mirror, meet at a point when produced backward.
(d) light of different colours make different images.

Question : The field of view is maximum for
(a) plane mirror
(b) concave mirror
(c) convex mirror
(d) cylindrical mirror

Question : A virtual image larger than the object can be obtained by
(a) concave mirror
(b) convex mirror
(c) plane mirror
(d) concave lens

Question : An object is placed 40 cm from a concave mirror of focal length 20 cm. The image formed is
(a) real, inverted and same in size
(b) real, inverted and smaller
(c) virtual, erect and larger
(d) virtual, erect and smaller

Question : All of the following statements are correct except
(a) the magnification produced by a convex mirror is always less than one
(b) a virtual, erect, same-sized image can be obtained using a plane mirror
(c) a virtual, erect, magnifield image can be formed using a concave mirror
(d) a real, inverted, same-sized image can be formed using a convex mirror.

Question : A person is six feet tall. How tall must a plane mirror be if he is able to see his entire length?
(a) 3 ft
(b) 4.5 ft
(c) 7.5 ft
(d) 6 ft

Question : The image formed by a concave mirror is
(a) always real
(b) always virtual
(c) certainly real if the object is virtual
(d) certainly virtual if the object is real

Question : In image formation from spherical mirrors, only paraxial rays are considered because they
(a) are easy to handle geometrically
(b) contain most of the intensity of the incident light
(c) form nearly a point image of a point source
(d) show minimum dispersion effect

Question : For reflection through spherical surfaces, the normal at the point of incidence is
(a) perpendicular to the principle axis and passes through the centre of curvature
(b) perpendicular to the focal plane and passes through the pole.
(c) perpendicular to the tangent plane at pole and passes through the focus.
(d) perpendicular to the tangent plane at the point of incidence and passes through the centre of curvature.

Question : The equation n2/v - n1/v = n2 - n1/R holds true for
(a) only concave mirror
(b) only convex mirror
(c) both concave and convex mirror
(d) any type of reflecting surface

Question : Which of the following (referred to a spherical mirror) depends on whether the rays are paraxial or not?
(a) Pole
(b) Focus
(d) Principal axis

Question : Which of the following is correct for the beam which enters the medium?
(a) Travel as a cylindrical beam
(b) Diverge
(c) Converge
(d) Diverge near the axis and converge near the periphery

Question : When light is refracted into a medium,
(a) its wavelength and frequency both increase
(b) its wavelength increases but frequency remains unchanged
(c) its wavelength decreases but frequency remains unchanged
(d) its wavelength and frequency both decrease

Question : When light is refracted, which of the following does not change ?
(a) Wavelength
(b) Frequency
(c) Velocity
(d) Amplitude

Question : If the light moving in a straight line bends by a small but fixed angle, it may be a case of
(a) reflection
(b) refraction
(c) diffraction
(d) both (a) & (b)

Question : Total internal reflection can take place only if
(a) light goes from optically rarer medium (smaller refractive index) to optically denser medium
(b) light goes from optically denser medium to rarer medium
(c) the refractive indices of the two media are close to different
(d) the refractive indices of the two media are widely different

Question : The difference between reflection and total internal reflection is that
(a) the laws of reflection hold true for reflection but not for total internal reflection.
(b) total internal reflection can take place only when light travels from a rarer medium to a denser medium while reflection can take place vice-versa also.
(c) reflection can take place when light travels from a rarer medium to denser medium and vice-versa but total internal reflection can take place only when it travels from an optically denser to an optically rarer medium.
(d) reflection is a natural phenomena while total internal reflection is man-made.

Question : When the angle of incidence of a light ray is greater than the critical angle it gets
(a) critically refracted
(b) totally reflected
(c) total internally reflected
(d) totally refracted

Question : Which of the following phenomena is used in optical fibres ?
(a) Total internal reflection
(b) Scattering
(c) Diffraction
(d) Refraction

Question : Critical angle of light passing from glass to water is minimum for
(a) red colour
(b) green colour
(c) yellow colour
(d) violet colour

Question : Which of the following is not due to total internal reflection?
(a) Working of optical fibre
(b) Difference between apparent and real depth of pond
(c) Mirage on hot summer days
(d) Brilliance of diamond

Question : Identify the wrong sign convention
(a) The magnification for virtual image formed by a convex lens is positive
(b) The magnification for real image formed by a convex lens is negative
(c) The height measured normal to the principal axis upwards is positive
(d) The magnification for virtual image formed by a concave lens is negative

Question : The apparent flattening of the sun at sunset and sunrise is due to
(a) refraction
(b) diffraction
(c) total internal reflection
(d) interference

Question : The speed of light in an isotropic medium depends on
(a) the nature of the source
(b) its wavelength
(c) its direction of propagation
(d) its intensity

Question : A parallel beam of light is incident on a converging lens parallel to its principal axis. As one moves away from the lens on the other side on its principal axis, the intensity of light
(a) remains constant
(b) continuously increases
(c) continuously decreases
(d) first increases then decreases

Question : The rays of different colours fail to converge at a point after going through a converging lens. This defect is called
(a) spherical aberration
(b) distortion
(c) coma
(d) chromatic aberration

Question : What causes chromatic aberration?
(a) Marginal rays
(b) Central rays
(c) Difference in radii of curvature of its surfaces
(d) Variation of focal length of lens with colour

Question : The focal length of a converging lens are fV and fR for violet and red light respectively. Then
(a) fV > fR
(b) fV = fR
(c) fV < fR
(d) any of the three is possible depending on the value of the average refractive index m

Question : A narrow beam of white light goes through a slab having parallel faces
(a) the light never splits in different colours
(b) the emergent beam is white
(c) the light inside the slab is split into different colours
(d) the light inside the slab is white

Question : Chromatic aberration in a lens is caused by
(a) reflection
(b) interference
(c) diffraction
(d) dispersion

Question : An astronomical telescope has a large aperture to
(a) reduce spherical aberration
(b) have high resolution
(c) increases span of observation
(d) have low dispersion

Question : The angular dispersion produced by a prism
(a) increases if the average refractive index increases
(b) increases if the average refractive index decreases
(c) remains constant whether the average refractive index increases or decreases
(d) has no relation with average refractive index.

Question : If a glass prism is dipped in water, its dispersive power
(a) increases
(b) decreases
(c) does not change
(d) may increase or decrease depending on whether the angle of the prism is less than or greater than 60º

Question :If D is the deviation of a normally falling light beam on a thin prism of angle A and δ is the dispersive power of the same prism then
(a) D is independent of A.
(b) D is independent of refractive Index.
(c) δ is independent of refractive index.
(d) δ is independent of A.

Question : When white light enters a prism, it gets split into its constituent colours. This is due to
(a) high density of prism material
(b) because μ is different for different wavelength
(c) diffraction of light
(d) velocity changes for different frequency

Question : Yellow light is refracted through a prism producing minimum deviation. If i1 and i2 denote the angle of incidence and emergence for this prism, then
(a) i1 = i2
(b) i1 > i2
(c) i1 < i2
(d) i1 + i2 = 90º

Question : By properly combining two prisms made of different materials, it is not possible to have
(a) dispersion without average deviation
(b) deviation without dispersion
(c) both dispersion and average deviation
(d) neither dispersion nor average deviation

Question : When the incidence angle is equal to the angle of emergence of light from the prism the refracted ray inside the prism
(a) becomes parallel to the right face of prism
(b) becomes perpendicular to the base of prism
(c) becomes parallel to the base of prism
(d) becomes perpendicular to the left face of prism

Question : The dispersive power of a prism depends on its
(a) shape
(b) size
(c) angle of prism
(d) refractive index of the monitorial of the prism

Question : The angle of prism is 60° and angle of deviation is 30°.In the position of minimum deviation, the values of angle of incidence and angle of emergence are:
(a) i = 45°; e = 50°
(b) i = 30°; e = 45°
(c) i = 45°; e = 45°
(d) i = 30°; e = 30°

Question : In primary rainbow what is the order of colours observed from earth ?
(a) Violet innermost, red outermost.
(b) Red innermost, violet outermost.
(c) Random.
(d) White and dark alternatively

Question : Which light rays undergoes two internal reflection inside a raindrop, which of the rainbow is formed?
(a) Primary rainbow
(b) Secondary rainbow
(c) Both (a) and (b)
(d) Can’t say

Question : In secondary rainbow what is the order of colours observed from earth?
(a) Violet innermost, red outermost.
(b) Red innermost, violet outer most.
(c) Random.
(d) White and dark alternatively.

Question : Identify the mismatch in the following
(a) Myopia - Concave lens
(b) For rear view - Concave mirror
(c) Hypermetropia - Convex lens
(d) Astigmatism - Cylindrical lens

Question : Astigmatism is corrected using
(a) cylindrical lens
(b) plano-convex lens
(c) plano-concave lens
(d) convex lens

Question : The focal length of a normal eye-lens is about
(a) 1 mm
(b) 2 cm
(c) 25 cm
(d) 1 m

Question : A normal eye is not able to see objects closer than 25 cm because
(a) the focal length of the eye is 25 cm
(b) the distance of the retina from the eye-lens is 25 cm
(c) the eye is not able to decrease the distance between the eye-lens and the retina beyond a limit
(d) the eye is not able to decrease the focal length beyond a limit

Question : The image formed by an objective of a compound microscope is
(a) real and diminished
(b) real and enlarged
(c) virtual and enlarged
(d) virtual and diminished

Question: Two thin lenses are in contact and the focal length of the combination is 80 cm. If the focal length of one lens is 20 cm, then the power of the other lens will be

(a) 1.66 D
(b) 4.00 D
(c) – 100 D
(d) – 3.75 D

Question: A plano-convex lens is made of material of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is

(a) 50 cm
(b) 100 cm
(c) 200 cm
(d) 400 cm

Question: A lens made of glass whose index of refraction is 1.60 has a focal length of + 20 cm in air. Its focal length in water, whose refractive index is 1.33, will be

(a) three times longer than in air
(b) two times longer than in air
(c) same as in air
(d) None of these

Question:  A convex lens is in contact with concave lens. The magnitude of the ratio of their powers is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths (in cm)?

(a) –15, 10
(b) –10, 15
(c) 75, 50
(d) –75, 50

Question:   A bi-convex lens made of glass (refractive index 1.5) is put in a liquid of refractive index 1.7. Its focal length will

(a) decrease and change sign
(b) increase and change sign
(c) decrease and remain of the same sign
(d) increase and remain of the same sign

Question:  The rays of different colours fail to converge at a point after going through a converging lens. This defect is called

(a) spherical aberration (b) distortion
(c) coma                        (d) chromatic aberration

Question:  What causes chromatic aberration?

(a) Marginal rays
(b) Central rays
(c) Difference in radii of curvature of its surfaces
(d) Variation of focal length of lens with colour

Question:  The angular dispersion produced by a prism

(a) increases if the average refractive index increases
(b) increases if the average refractive index decreases
(c) remains constant whether the average refractive index increases or decreases
(d) has no relation with average refractive index.

Question: If a glass prism is dipped in water, its dispersive power

(a) increases
(b) decreases
(c) does not change
(d) may increase or decrease depending on whether the

Question: The image formed by an objective of a compound microscope is
(a) real and diminished
(b) real and enlarged
(c) virtual and enlarged
(d) virtual and diminished

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