Huygens’ theory
Q.1 which among the following isn’t a suitable phenomenon to establish that light is wave motion?
a) Interference
b) Diffraction
c) Reflection
d) Polarization
Answer-c)
Concept: Light undergoes interference, diffraction, and polarization. These phenomena establish that light is a wave motion. Therefore, out of the options, reflection isn’t a suitable phenomenon to establish that light is wave motion.
Q.2 The optical path of monochromatic light is the same if it travels 2 cm thickness of glass or 2.25 cm thickness of water. If the refractive index of water is 1.33, what is the refractive index of glass?
a) 2.5
b) 1.5
c) 3.5
d) 4.5
Answer: b
Q.3 Identify the condition which is not necessary for two light waves to be coherent.
a) The two waves must be continuous
b) The two waves should be of the same frequency or wavelength
c) They should have a constant or zero phases difference
d) They two light sources should be narrow
Answer: d
Concept: The essential conditions for two light waves to be coherent includes that the two waves must be continuous, the two waves should be of the same frequency or wavelength, and they should have a constant or zero phases difference. So, the unnecessary condition for two light waves to be coherent is the statement that the sources should be narrow.
Q.4 In Huygens’ theory, light waves are longitudinal and do not require a material medium for their propagation.
a) True
b) False
Answer: b
Concept: In Huygens’ theory, light waves are longitudinal and require a material medium for their propagation. That is why, Huygens’ assumed the existence of an all-pervading hypothetical medium, called ether.
Q.5 The speed of yellow light in a certain liquid is 2.4 × 108 m/s. Find the refractive index of the liquid.
a) 1.25
b) 5.55
c) 6.25
d) 12.25
Answer – a)