Question

When light waves suffers reflection at the interface from air to glass, the change in phase of reflected waves is equal to:
A $0$
B $\dfrac{\pi }{2}$
C $\pi $
D $2\pi $

Answer 1

Hint As we know reflection of the wave takes place when a light wave falls on the surface, and definitely there would be an angle of reflection as the refractive index of air and glass are different and glass is denser than air.

Complete Step By Step Solution
Reflection of light wave: the reflection of light happens when light waves fall on the surface and that surface can’t absorb the energy of light waves then the light waves get reflected at a certain angle, known as angle of reflection.
The angle of reflection: The angle between the reflected wave and normal is known as the angle of reflection. The angle of reflection depends on the refractive index of the material.
Refractive index: refractive index of a material tells us how fast a light wave can travel in a particular material. The Refractive index is a dimensionless number.
Now, come to the question, when a light wave suffers reflection at the interface from air to glass, it experiences a change in phase because the refractive index of glass is more than air, as we know that air is a rarer medium and glass is denser medium. So, the change in phase of the reflected wave is $\pi $.

Hence, option C is the right answer

Note The point to be noted is we should know that when a light wave travels from rarer to denser than the phase of the incident wave change with angle $\pi $ and when it travels from denser to rare then the phase of the incident wave does not change.