# Physics class 12 chapter 10 Objective Questions

## Wave Optics Objective Questions

1. The idea of secondary wavelets for the. propagation of a wave was first given by

(A) Newton

(B) Huygens

(C) Maxwell

(D) Fresnel

1. Light propagates rectilinearly, due to

(A) wave nature

(B) wavelengths

(C) velocity

(D) frequency

1. Which of the following is correct for light diverging from a point source?

(A) The intensity decreases in proportion with the distance squared.

(B) The wavefront is parabolic.

(C) The intensity at the wavelength does not depend on the distance.

(D) None of these.

Answer: (A) The intensity decreases in proportion with the distance squared.

1. 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

1. The phenomena which is not explained by Huygen’s construction of wavefront

(A) reflection

(B) diffraction

(C) refraction

(D) origin of spectra

1. 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.

1. Two slits in Young’s double slit experiment have widths in the ratio 81 :1. The ratio of the amplitudes of light waves is

(A) 3 :1

(B) 3 : 2

(C) 9 :1

(D) 6:1

1. When interference of light takes place

(A) energy is created in the region of maximum intensity

(B) energy is destroyed in the region of maximum intensity

(C) conservation of energy holds good and energy is redistributed

(D) conservation of energy does not hold good

Answer: (C) conservation of energy holds good and energy is redistributed

1. In a double slit interference pattern, the first maxima for infrared light would be

(A) at the same place as the first maxima for green light

(B) closer to the centre than the first maxima for green light

(C) farther from the centre than the first maxima for green light

(D) infrared light does not produce an interference pattern

Answer: (C) farther from the centre than the first maxima for green light

1. To observe diffraction, the size of the obstacle

(A) should beX/2, where X is the wavelength.

(B) should be of the order of wavelength.

(C) has no relation to wavelength.

(D) should be much larger than the wavelength.

Answer: (B) should be of the order of wavelength.

1. The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 A is of the order of

1. An optically active compound

(A) rotates the plane of polarised light

(B) changes the direction of polarised light

(C) does not allow plane polarised light to pass through

(D) none of these

Answer: (A) rotates the plane of polarised light

1. The reason of blue colour of the sky is

(A) scattering

(B) interference

(C) Polarization

(D) diffraction

1. The dark lines in solar spectrum are known as

(A) Fraunofer lines

(B) Telluric lines

(C) Both (A) and (B)

(D) None of these

1. Pure spectrum can be obtained using

(A) microscope

(B) spherometer

(C) spectrometer

(D) prism only

1. In the spectrum of white light obtained by a prism, the colour showing minimum deviation is

(A) yellow

(B) red

(C) blue

(D) violet

1. 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

Answer: (C) at infinite distance form the source

1. In a plane polarised light, the vector of electric field intensity vibrate in

(A) all directions

(B) a single plane

(C) mutually perpendicular directions

(D) None of these

1. A soap bubble appears colourful in white light because of

(A) polarization of light

(B) scattering of light

(C) refraction of light

(D) interference of light

1. Two virtual and coherent sources are produced in

(A) Young’s double-slit experiment

(B) Lyod mirror

(C) Fresnel’s biprism

(D) all of these

1. Huygens secondary wave principle is used to

(A) new geometrical position of the wavefront

(B) explain the superposition principle of waves

(C) explain the interference of light

(D) explain the polarization of light

Answer: (A) new geometrical position of the wavefront

1. Light consists of vibrations of

(A) Ether particles

(B) air particles

(C) electric and magnetic fields

(D) None of these

Answer: (C) electric and magnetic fields

1. According to wave motion-theory of light, the colour of light is decided by

(A) amplitude

(B) speed of wave

(C) frequency

(D) wavelength

1. The concept of secondary wavelets was given by

(A) Fresnel

(B) Maxwell

(C) Huygens

(D) Newton

1. When a polaroid is rotated about the incident beam, the intensity of light passed does not change. It so happens when the incident beam of light is

(A) fully plane polarized

(B) partly plane polarized

(C) unpolarized

(D) None of these

1. 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

Answer: (D) they have constant phase difference

1. The tangent of polarization angle is equal to the refractive index. This law is known as

(A) Malus law

(B) Brewster’s law

(C) Bragg’s law

(D) Compton’s law

1. If the wavelength of light in Young’s experiment is doubled, the fringe width

(A) remains the same

(B) gets doubled to

(C) is halved

1. The colour of a thin film is due to

(A) scattering

(B) interference

(C) dispersion

(D) diffraction