NEET Physics Wavefront Interference of Light Coherent and Incoherent Sources of Light MCQs Set A

a) phase

b) amplitude

c) period

d) frequency

Answer: phase

Question: A plane wave passes through a convex lens. The geometrical shape of the wavefront that emerges is

a) converging spherical

b) plane

c) diverging spherical

d) None of these

Answer: converging spherical

Question: Huygen’s concept of secondary wave

a) is a geometrical method to find a wavefront

b) allows us to find the focal length of a thick lens

c) is used to determine the velocity of light

d) is used to explain polarisation

Answer: is a geometrical method to find a wavefront

Question: The phenomena which is not explained by Huygen’s construction of wavefront is

a) origin of spectra

b) diffraction

c)  reflection

d) refraction

Answer: origin of spectra

Question:  Two sources of light are said to be coherent, when they give light waves of same

a) wavelength and constant phase difference

b) intensity and wavelength

c) amplitude and phase

d) phase and speed

Answer: wavelength and constant phase difference

Question: The colour of bright fringe nearest to central achromatic fringe in the interference pattern with white light will be

a) violet

b) red

c) green

d) yellow

Answer: violet

Question: The interfering fringes formed by a thin oil film on water are seen in yellow light of sodium lamp. We find the fringes

a) coloured

b) black and white

c) yellow and black

d) coloured without yellow

Answer: coloured

Question: Two coherent sources of intensity ratio 1 : 4 produce an interference pattern. The fringe visibility will be

a) 0.8

b) 0.4

c) 0.6

d) 1

Answer: 0.8

Question: Which of the following is correct for light diverging from a point source?

a) The intensity decreases in proportion for the distance squared.

b) The wavefront is parabolic

c) The intensity at the wavelingth does depend of the distance

d) None of these.

Answer:  The intensity decreases in proportion for the distance squared.

Question:  Shape of wavefront in case of
I. light diverging from a point source is spherical
II. light emerging out of a convex lens when a point source is placed at its focus is plane
III. the portion of the wavefront of light from a distant star intercepted by the Earth is plane.
Which of the above statements are correct?

a) II and III

b) I, II and III

c) I and II

d) I and III

Answer: II and III

Question: The principle of superposition is basic to the phenomenon of

a) interference

b) refraction

c) Polarisation

d) reflection

Answer:  interference

Question: Assertion : No interference pattern is detected when two coherent sources are infinitely close to each other.
Reason : The fringe width is inversely proportional to the distance between the two sources.

a) Assertion is correct, reason is correct; reason is a correct explanation for assertion

b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

c) Assertion is correct, reason is incorrect

d) Assertion is incorrect, reason is correct

Answer: Assertion is correct, reason is correct; reason is a correct explanation for assertion

Question: A point p is situated 90.50 and 90.58 cm away from two coherent sources. The nature of illumination of the point ‘p’ if the wavelength of light is 4000 Å, is

a) bright

b) dark

c) none of these

d) neither bright nor dark

Answer:  bright