A light ray of angles of incidence `40^(@)` emerged from the prism in minimum deviation position. Then what is the angle of incidence on the second surface ?

Options

A. `90^(@)`
B. `0^(@)`
C. `40^(@)`
D. `20^(@)`

Answer

To solve the problem, we need to understand the behavior of light as it passes through a prism, particularly under the condition of minimum deviation.

### Step-by-Step Solution:

1. **Identify the Given Information**:
- The angle of incidence (I) on the first surface of the prism is given as 40 degrees.
- The light ray emerges from the prism in a minimum deviation position.

2. **Understand Minimum Deviation Condition**:
- In the minimum deviation condition, two important relationships hold:
- The angle of incidence (I) is equal to the angle of emergence (E).
- The angle of refraction at the first surface (r1) is equal to the angle of refraction at the second surface (r2).

3. **Apply the Minimum Deviation Condition**:
- Since the angle of incidence (I) is equal to the angle of emergence (E), we can write:
\[ E = I \]
- Given that the angle of incidence (I) is 40 degrees, we can substitute this value:
\[ E = 40^\circ \]

4. **Conclusion**:
- Therefore, the angle of incidence on the second surface of the prism is also 40 degrees.

### Final Answer:
The angle of incidence on the second surface is \( 40^\circ \).