The change in phase, if a wave is reflected at a less dense surface, is

Options

A. zero
B. `pi` radian
C. `(pi)/(2)` radian
D. `(2pi)/(3)` radian

Answer

To solve the question regarding the change in phase when a wave is reflected at a less dense surface, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Wave Reflection**: When a wave travels from one medium to another, its behavior upon reflection can vary depending on the densities of the two media involved.

2. **Identify the Mediums**: In this case, we are dealing with a wave reflecting off a less dense medium. This means the wave is moving from a denser medium to a less dense medium.

3. **Phase Change Rules**:
- When a wave reflects off a more dense medium, it undergoes a phase change of π radians (or 180 degrees).
- Conversely, when a wave reflects off a less dense medium, there is no phase change, which means the phase change is 0 radians.

4. **Conclusion**: Therefore, for a wave reflecting off a less dense medium, the change in phase is 0 radians.

### Final Answer:
The change in phase, if a wave is reflected at a less dense surface, is **0 radians**.

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