Question

Statement-1: When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of π.

Statement-2: The centre of the interference pattern is dark

A. Statement-1 is true, statement-2 is true: Statement-2 is a correct explanation for statement-1
B. statement-1 is false, statement-2 is true
C. Statement-1 is true, Statement-2 is false.
D. statement-1 is true, statement-2 is true and statement-2 is not the correct explanation of statement-1

Answer 1

The statement that a phase change of π occurs upon reflection from an air-glass interface is true, provided the glass has a higher index of refraction than air, impacting optics phenomena like thin-film interference.

Step-by-step explanation:

When light reflects from the air-glass plate interface, a phase change of π (180° or a λ/2 shift) occurs if the index of refraction of glass (n₂) is greater than that of air (n₁). This phase change is significant as it affects phenomena like thin-film interference, where the path length and refractive indices are crucial factors. Typically, no phase change happens when light reflects from a medium with a lower refractive index.

In thin-film interference, variations in film thickness and composition can cause different wavelengths of light to interfere constructively or destructively, leading to the observation of various colors. The phase changes upon reflection can either enhance or reduce the interference effect, which is why the knowledge of these phase changes is key in optics.