When light wave suffers reflection at the interface from air to glass, the change in phase of the reflected wave is equal to

Options

A. zero
B. `pi/2`
C. `pi`
D. `2pi`

Explanation

To solve the question about the change in phase of a light wave when it reflects at the interface from air to glass, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Situation**:
- We have a light wave traveling from air (a less dense medium) to glass (a denser medium). When light reflects off a boundary between two different media, it can undergo a phase change.

2. **Identify the Phase Change Rule**:
- When light reflects off a boundary where it is moving from a less dense medium (air) to a denser medium (glass), there is a phase change of π (or 180 degrees) for the reflected wave.

3. **Wave Equation Representation**:
- The incident wave can be represented as:
\[ A_I = A \sin(\omega t - kx) \]
- Upon reflection, the reflected wave will undergo a phase change of π, which can be represented as:
\[ A_R = A \sin(\omega t - kx + \pi) \]
- This phase change indicates that the reflected wave is inverted.

4. **Conclusion**:
- Therefore, the change in phase of the reflected wave when light reflects from air to glass is equal to π.

5. **Final Answer**:
- The change in phase of the reflected wave is π (option 3).