# Wave Optics MCQ Class 12 Physics

Please refer to Chapter 10 Wave Optics MCQ Class 12 Physics with answers below. These multiple-choice questions have been prepared based on the latest NCERT book for Class 12 Physics. Students should refer to MCQ Questions for Class 12 Physics with Answers to score more marks in Grade 12 Physics exams. Students should read the chapter Wave Optics and then attempt the following objective questions.

## MCQ Questions Class 12 Physics Chapter 10 Wave Optics

The Wave Optics MCQ Class 12 Physics provided below covers all important topics given in this chapter. These MCQs will help you to properly prepare for exams.

Question. Light propagates rectilinearly, due to
(a) wave nature
(b) wavelengths
(c) velocity
(d) frequency

A

Question. When a polaroid is rotated, the intensity of light varies but never reduces to zero. It shows that the incident light is:
(a) unpolarised
(b) completely plane polarised
(c) partially plane polarised
(d) None of the above

C

Question. The minimum value of the refractive index is:
(a) zero
(b) 1
(c) less than 1 but not zero
(d) more than 1

C

Question. If Young’s double slit experiment is performed in water keeping the rest of the set-up same, the fringes will
(a) increase in width
(b) decrease in width
(c) remain unchanged
(d) not be formed

B

Question. A laser beam is used for locating distant objects because
(a) it is monochromatic
(b) it is not chromatic
(c) it is not observed
(d) it has small angular spread.

D

Question. For sustained interference, we need two sources which emit radiations :
(a) of the same intensity
(b) of the same amplitude
(c) having a constant phase difference
(d) None of these

C

Question. The locus of all particles in a medium, vibrating in the same phase is called
(a) wavelet
(b) fringe
(c) wave front
(d) None of these

C

Question. In Young’s double slit experiment, the central point on the screen is:
(a) bright
(b) dark
(c) first bright and later dark
(d) first dark and later bright

A

Question. Poisson’s bright spot was discovered by:
(a) Fresnel
(b) Rayleigh
(c) Poisson
(d) Fraunhoffer

C

Question. A plane wave passes through a convex lens. The geometrical shape of the wavefront that emerges is
(a) plane
(b) diverging spherical
(c) converging spherical
(d) None of these

C

Question. The fringe width in a Young’s double slit experiment can be increased if we decrease
(a) width of slits
(b) separation of slits
(c) wavelength of light used
(d) distance between slits and screen

A

Question. The device which produces highly coherent sources is
(a) Fresnel biprism
(b) Young’s double slit
(c) Laser
(d) Lloyd’s mirror

C

Question. Which of the following is conserved when light waves interefere?
(a) phase
(b) intensity
(c) amplitude
(d) none of these

D

Question. The refractive index of glass is 1.5 for light waves of X = 6000 A in vacuum. Its wavelength in glass is
(a) 2000 Å
(b) 4000 Å
(c) 1000 Å
(d) 3000 Å

B

Question. If the width of the slit in single slit diffraction experiment is doubled, then the central maximum of diffraction pattern becomes
(b) sharper and brighter
(c) sharper and fainter

B

Question. The idea of secondary wavelets for the. propagation of a wave was first given by
(a) Newton
(b) Huygens
(c) Maxwell
(d) Fresnel

B

Question. Polaroid glass is used in sun glasses because
(a) it reduces the light intensity to half on account of polarisation
(b) it is fashionable
(c) it has good colour
(d) it is cheaper.

A

Question. Intensity of light depends on
(a) amplitude
(b) frequency
(c) wavelength
(d) velocity

A

Question. A person cannot see object clearly beyond 50 cm. The pow er of the lens to correct his vision is :
(a) +0.5 dioptre
(b) -0.5 dioptre
(c) -2 dioptre
(d) +2 dioptre

C

Question. The colours on the soap bubble is due to
(a) Interference
(b) Polarisation
(c) Diffraction
(d) Reflection

A

Question. From Brewster’s law of polarisation, it follows that the anlge of polarisaiton depends upon
(a) the wavelength of light
(b) plane of polarisation’s orientation
(c) plane of vibration’s orientation
(d) None of these

A

Question. When monochromatic light is replaced by white light in Fresnel’s biprism arrangement, the central fringe is
(a) coloured
(b) white
(c) dark
(d) None of these

B

Question. The focal length of the lens is 50 cm; then its power is:
(a) +2D
(b) +1D
(c) -2D
(d) -1D

A

Question. If a wave undergoes refraction, what will be the phase change?
(a) 180°
(b) 270°
(c) 90°
(d) 0°

D

Question. Bonding of light rays at sharp obstacles is called :
(a) Refraction
(b) Diffraction
(c) Interference
(d) Polarisation

B

Question. The electromagnetic wave theory of light fails to explain :
(a) compton effect
(b) photoelectric effect
(c) neither (a) nor (b)
(d) Both (a) and (b)

A

Question. Light consists of vibrations of
(a) Ether particles
(b) air particles
(c) electric and magnetic fields
(d) None of these

C

Question. Transverse nature of light was confirmed by the phenomenon of
(a) refreaction of light
(b) diffraction of light
(c) dispersion of light
(d) polarization of light

D

Question. A rainbow is a natural example of
(a) refraction of light
(b) reflection of light
(c) refraction, reflection and dispersion of light
(d) None of these

C

Question. Two sources of waves are said to be coherent of
(a) their amplitudes are equal
(b) they produce waves of equal wavelengths
(c) they produce waves of equal velocities
(d) they have constant phase difference

D

Question. The angle of minimum deviation of a prism depends upon the aggie of:
(a) incidence
(b) reflection
(c) prism
(d) none of these

C

Question. Which of the following phenomenon is not explained by Huygen’s wave theory?
(a) Diffraction
(b) Interference
(c) Polarisation
(d) Photoelectric effect

D

Question. Optical fibre communication is based on which of the following phenomena :
(a) Total Internal reflection
(b) Scattering
(c) Reflection
(d) Interference

A

Question. The phenomena which is not explained by Huygen’s construction of wavefront
(a) reflection
(b) diffraction
(c) refraction
(d) origin of spectra

D

Question. Polarisation phenomenon explains which nature of light?
(a) Transverse
(b) longitudinal
(c) Both transverse and longitudinal
(d) geometrical

A

Question. In Young’s double-slit experiment, the phase difference between the light waves reaching the third bright fringe from the central fringe will be (λ=6000 Å)
(a) Zero
(b) 2π
(c) 4π
(d) 6π

D

Question. The reason of blue colour of the sky is
(a) scattering
(b) interference
(c) Polarization
(d) diffraction

A

Question. In Fraunhofer class of diffraction, the source of light is placed
(a) at finite distance from the obstacle
(b) in close contact with the source
(c) at infinite distance form the source
(d) None of these

C

Question. How does the diffraction band of blue light look in comparison with the red light? B
(a) No changes
(b) Diffraction pattern becomes narrower
(d) Diffraction pattern disappears

B

Question. Unpolarised light of intensity 32 W m–2 passes through three polarizers such that the transmission axis of the last polarizer is crossed with that of the first. The intensity of final emerging light is 3 W m–2. The intensity of light transmitted by first polarizer will be
(a) 32 W m–2
(b) 16 W m–2
(c) 8 W m–2
(d) 4 W m–2

B

Question. Aperture of the human eye is 2 mm. Assuming the mean wavelength of light to be 5000 Å, the angular resolution limit of the eye is nearly
(a) 2 minute
(b) 1 minute
(c) 0.5 minute
(d) 1.5 minute

B

Question. In Young’s double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ1 = 12000Å and λ 2 = 10000Å. 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) 6 mm
(b) 4 mm
(c) 3 mm
(d) 8 mm

A

Question. With a monochromatic light, the fringe-width obtained in a Young’s double slit experiment is 0.133 cm. The whole setup is immersed in water of refractive index 1.33, then the new fringe-width is
(a) 0.133 cm
(b) 0.1 cm
(c) 1.33 × 1.33 cm
(d) (1.22/2) cm

B

Question. In Young’s double slit experiment with sodium vapour lamp of wavelength 589 nm and the slits 0.589 mm apart, the half angular width of the central maximum is
(a) sin–1 (0.01)
(b) sin–1 (0.0001)
(c) sin–1 (0.001)
(d) sin–1 (0.1)

C

Question. Two sources of light of wavelengths 2500 Å and 3500 Å are used in Young’s double slit expt. simultaneously. Which orders of fringes of two wavelength patterns coincide?
(a) 3rd order of 1st source and 5th of the 2nd
(b) 7th order of 1st and 5th order of 2nd
(c) 5th order of 1st and 3rd order of 2nd
(d) 5th order of 1st and 7th order of 2nd

B

Question. In Young’s double slit experiment with sodium vapour lamp of wavelength 589 nm and the slits 0.589 mm apart, the half angular width of the central maximum is
(a) sin–1 0.01
(b) sin
(c) sin–1 0.001
(d) sin–1 0.1

C

Question. A slit of width a is illuminated by white light. The first minimum for red light (l = 6500 Å) will fall at q = 30º when a will be
(a) 3250 Å
(b) 6.5 × 10–4 cm
(c) 1.3 micron
(d) 2.6 × 10–4 cm

C

Question. A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct ?
(a) The angular width of the central maximum of the diffraction pattern will increase.
(b) The angular width of the central maximum will decrease.
(c) The angular width of the central maximum will be unaffected.
(d) Diffraction pattern is not observed on the screen in case of electrons.

B

Question. If the polarizing angle of a piece of glass for green light is 54.74°, then the angle of minimum deviation for an equilateral prism made of same glass is [Given, tan 54.74° = 1.414]
(a) 45°
(b) 54.74°
(c) 60°
(d) 30°

D

Question. A parallel beam of monochromatic unpolarised light is incident on a transparent dielectric plate of refractive index The reflected beam is completely polarised. Then the angle of incidence is
(a) 30º
(b) 60º
(c) 45º
(d) 75º