# MCQs For NCERT Class 12 Physics Chapter 10 Wave Optics

Please refer to the MCQ Questions for Class 12 Physics Chapter 10 Wave Optics with Answers. The following Wave Optics Class 12 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 12. Our experts have designed MCQ Questions for Class 12 Physics with Answers for all chapters in your NCERT Class 12 Physics book.

## Wave Optics Class 12 MCQ Questions with Answers

See below Wave Optics Class 12 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. The frequency of a light wave in a material is 2 × 1014 Hz and wavelength is 5000 Å. The refractive index of material will be
(a) 1.50
(b) 3.00
(c) 1.33
(d) 1.40

B

Question. An electromagnetic radiation of frequency n, wavelength l, travelling with velocity v in air, enters a glass slab of refractive index m. The frequency, wavelength and velocity of light in the glass slab will be respectively
(a) n, 2λ and v/μ
(b) 2n/μ, λ/μ and v
(c) n, λ/μ and v/μ

D

Question. Unpolarised light is incident from air on a plane surface of a material of refractive index m. At a particular angle of incidence i,it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation?
(a) Reflected light is polarised with its electric vector parallel to the plane of incidence.
(b) Reflected light is polarised with its electric vector perpendicular to the plane of incidence.
(c) i =sin−1(1/μ)
(d) i = tan−1(1/μ)

B

Question. Two polaroids P1 and P2 are placed with their axis perpendicular to each other. Unpolarised light I0 is incident on P1. A third polaroid P3 is kept in between P1 and P2 such that its axis makes an angle 45° with that of P1. The intensity of transmitted light through P2 is
(a) I0/4
(b) I0/8
(c) I0/16
(d) I0/2

B

Question. Which of the phenomenon is not common to sound and light waves ?
(a) Interference
(b) Diffraction
(c) Coherence
(d) Polarisation

D

Question. The refractive index of water is 1.33. What will be the speed of light in water?
(a) 4 × 108 m/s
(b) 1.33 × 108 m/s
(c) 3 × 108 m/s
(d) 2.25 × 108 m/s

D

Question. Light travels through a glass plate of thickness t and having a refractive index m. If c is the velocity of light in vacuum, the time taken by light to travel this thickness of glass is
(a) t/μc
(b) μt /c
(c) tμc
(d) tc /μ

B

Question. Ray optics is valid, when characteristic dimensions are
(a) much smaller than the wavelength of light
(b) of the same order as the wavelength of light
(c) of the order of one millimetre
(d) much larger than the wavelength of light.

D

Question. A star, which is emitting radiation at a wavelength of 5000 Å, is approaching the earth with a velocity of 1.5 × 104 m/s. The change in wavelength of the radiation as received on the earth is
(a) 25 Å
(b) 100 Å
(c) zero
(d) 2.5 Å

A

Question. A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5. The wavelength of refracted light will be
(a) depend on intensity of refracted light
(b) same
(c) smaller
(d) larger.

C

Question. In a Young’ double slit experiment if there is no initial phase difference between the light from the two slits, a point on the screen corresponding to the fifth minimum has path difference.
(a) 5.λ/2
(b) 10.λ/2
(c) 9.λ/2
(d) 11.λ/2

C

Question. Interference is possible in
(a) light waves only
(b) sound waves only
(c) both light and sound waves
(d) neither light nor sound waves.

C

Question. In a Fresnel biprism experiment, the two positions of lens give separation between the slits as 16 cm and 9 cm respectively. What is the actual distance of separation?
(a) 13 cm
(b) 14 cm
(c) 12.5 cm
(d) 12 cm

D

Question. Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is 3/2 is
(a) 2 × 10–4 s
(b) 2 × 108 s
(c) 2 × 10–11 s
(d) 2 × 1011 s

C

Question. In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes
(a) double
(b) half
(c) four times
(d) one-fourth

C

Question. In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be 0.2°. What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water? (mwater = 4/3)
(a) 0.1°
(b) 0.266°
(c) 0.15°
(d) 0.05°

C

Question. The intensity at the maximum in a Young’s double slit experiment is I0. Distance between two slits is d = 5l, where l is the wavelength of light used in the experiment. What will be the intensity in front of one of the slits on the screen placed at a distance D = 10d ?
(a)  3/4 I0
(b) I0 /2
(c) I0
(d)  I0 /4

B

Question. Two slits in Young’s experiment have widths in the ratio 1 : 25. The ratio of intensity at the maxima and minima in the interference pattern, Imax /Imin is
(a) 49/121
(b) 4/9
(c) 9/4
(d) 121/49

C

Question. In the Young’s double slit experiment, the intensity of light at a point on the screen where the path difference l is K, (l being the wavelength of light used). The intensity at a point where the path difference is l/4 will be
(a) K
(b) K/4
(c) K/2
(d) zero

C

Question. A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometre from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å, is of the order of
(a) 0.5 m
(b) 5 m
(c) 5 mm
(d) 5 cm

C

Question. A parallel beam of light of wavelength l is incident normally on a narrow slit. A diffraction pattern formed on a screen placed perpendicular to the direction of the incident beam. At the second minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of slit is
(a) 2p
(b) 3p
(c) 4p
(d) pl

C

Question. Which one of the following phenomena is not explained by Huygen’s construction of wavefront ?
(a) Refraction
(b) Reflection
(c) Diffraction
(d) Origin of spectra

D

Question. In Young’s double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths l1 = 12000 Å and l2 = 10000 Å. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other?
(a) 4 mm
(b) 3 mm
(c) 8 mm
(d) 6 mm

D

Question. In a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used.
What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern?
(a) 0.5 mm
(b) 0.02 mm
(c) 0.2 mm
(d) 0.1 mm

C

Question. Colours appear on a thin soap film and on soap bubbles due to the phenomenon of
(a) interference
(b) dispersion
(c) refraction
(d) diffraction.

A

Question. Interference was observed in interference chamber where air was present, now the chamber is evacuated, and if the same light is used, a careful observer will see
(a) no interference
(b) interference with brighter bands
(c) interference with dark bands
(d) interference with larger width.

D

Question. Green light of wavelength 5460 Å is incident on an air-glass interface. If the refractive index of glass is 1.5, the wavelength of light in glass would be (c = 3 × 108 m s–1)
(a) 3640 Å
(b) 5460 Å
(c) 4861 Å
(d) none of these.

A

Question. In Young’s double slit experiment, the fringes width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4/3, without disturbing the geometrical arrangement, the new fringe width will be
(a) 0.30 mm
(b) 0.40 mm
(c) 0.53 mm
(d) 450 micron.

A

Question. In Young’s double slit experiment the separation d between the slits is 2 mm, the wavelength l of the light used is 5896 Å and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.20°. To increase the fringe angular width to 0.21° (with same l and D) the separation between the slits needs to be changed to
(a) 1.8 mm
(b) 1.9 mm
(c) 2.1 mm
(d) 1.7 mm

B

Question. If yellow light emitted by sodium lamp in Young’s double slit experiment is replaced by monochromatic blue light of the same intensity
(a) fringe width will decrease
(b) fringe width will increase
(c) fringe width will remain unchanged
(d) fringes will becomes less intense

A

Question. A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm.
The aperture is illuminated normally by a parallel beam of wavelength 5 × 10–5 cm. The distance of the first dark band of the diffraction pattern from the centre of the screen is

(a) 0.10 cm
(b) 0.25 cm
(c) 0.20 cm
(d) 0.15 cm

D

Question. In Young’s double slit experiment the distance between the slits and the screen is doubled. The separation between the slits is reduced to half. As a result the fringe width
(a) is halved
(b) becomes four times
(c) remains unchanged
(d) is doubled.

B

Question. Young’s double slit experiment is first performed in air and then in a medium other than air. It is found that 8th bright fringe in the medium lies where 5th dark fringe lies in air. The refractive index of the medium is nearly
(a) 1.59
(b) 1.69
(c) 1.78
(d) 1.25

C

Question. The Young’s double slit experiment is performed with blue and with green light of wavelengths 4360 Å and 5460 Å respectively. If x is the distance of 4th maxima from the central one, then
(a) x(blue) = x(green)
(b) x(blue) > x(green)
(c) x(blue) < x(green)
(d) x(blue)/x(green) = 5460/4360

C

Question. Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m is

A

Question. Ratio of intensities of two waves are given by 4 : 1.Then ratio of the amplitudes of the two waves is
(a) 2 : 1
(b) 1 : 2
(c) 4 : 1
(d) 1 : 4

A

Question. An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of
(a) small focal length and large diameter
(b) large focal length and small diameter
(c) large focal length and large diameter
(d) small focal length and small diameter.

C

Question. Diameter of human eye lens is 2 mm. What will be the minimum distance between two points to resolve them, which are situated at a distance of 50 meter from eye? (The wavelength of light is 5000 Å.)
(a) 2.32 m
(b) 4.28 mm
(c) 1.25 cm
(d) 12.48 cm

C

Question. The ratio of resolving powers of an optical microscope for two wavelengths l1 = 4000 Å and l2 = 6000 Å is
(a) 9 : 4
(b) 3 : 2
(c) 16 : 81
(d) 8 : 27

B

Question. A parallel beam of monochromatic light of wavelength 5000 Å is incident normally on a single narrow slit of width 0.001 mm. The light is focussed by a convex lens on a screen placed in focal plane.
The first minimum will be formed for the angle of diffraction equal to
(a) 0°
(b) 15°
(c) 30°
(d) 50°

C

Question. The Brewsters angle ib for an interface should be
(a) 0° < ib < 30°
(b) 30° < ib < 45°
(c) 45° < ib < 90°
(d) ib = 90°

C

Question. The colours seen in the reflected white light from a thin oil film are due to
(a) diffraction
(b) interference
(c) polarisation
(d) dispersion

B

Question. The idea of the quantum nature of light has emerged in an attempt to explain
(a) interference
(b) diffraction
(b) polarization
(d) radiation spectrum of a black body

D

Question. To demonstrate the phenomenon of interference, we require two sources which emit radiation of
(a) nearly the same frequency
(b) the same frequency
(c) different wavelengths
(d) the same frequency and having a definite phase relationship

D

Question. Which of the following phenomena is not common to sound and light waves ?
(a) Interference
(b) Diffraction
(c) Coherence
(d) Polarisation

D

Question. The contrast in the fringes in an interference pattern depends on
(a) fringe width
(b) wavelength
(c) intensity ratio of the sources
(d) distance between the slits

Question. Which of the following cannot be polarised ?
(b) b rays
(c) Infrared rays
(d) g rays

Question. If the intensities of the two interfering beams in Young’s double-slit experiment are I1 and I2, then the contrast between the maximum and minimum intensities is good when
(a) | I1 and I2 | is large
(b) | I1 and I2 | is small
(c) either I1 or I2 is zero
(d) I1 = I2

D

Question. Polarisation of light establishes
(a) corpuscular theory of light
(b) quantum nature of light
(c) transverse nature of light
(d) all of the three