When light wave passes from a medium of refractive index ' ' to another medium of refractive index ' 2 ' the phase change occurs to the light is :

Step-by-step solution

When light passes (transmits) from one medium into another, the transmitted wave undergoes no phase change, regardless of whether it enters a denser or rarer medium. A phase change of 180° occurs only during reflection at a boundary with a denser medium — not during transmission. Since the light here is passing (transmitting) from medium into medium 2 , the phase change is zero.