If a ray of light is incident on a plane mirror at an angle of incidence of `30^@`, then deviation produced by the mirror is

Options

A. `15^@`
B. `30^@`
C. `60^@`
D. `120^@`

Explanation

To solve the problem of finding the deviation produced by a plane mirror when a ray of light is incident at an angle of incidence of \(30^\circ\), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Law of Reflection**:
The law of reflection states that the angle of incidence (\(i\)) is equal to the angle of reflection (\(r\)). Therefore, if the angle of incidence is \(30^\circ\), the angle of reflection will also be \(30^\circ\).

\[ i = r = 30^\circ \]

2. **Identify the Original and Final Path**:
The original path of the light ray is a straight line before it hits the mirror. After reflecting off the mirror, the light ray takes a new path. The deviation is the angle between the original path and the final path of the light ray.

3. **Calculate the Total Deviation**:
The total deviation (\(\Delta\)) caused by the mirror can be calculated using the formula:
\[ \Delta = 180^\circ - 2i \]
Here, \(i\) is the angle of incidence.

4. **Substitute the Angle of Incidence**:
Substitute \(i = 30^\circ\) into the deviation formula:
\[ \Delta = 180^\circ - 2 \times 30^\circ \]

5. **Perform the Calculation**:
Calculate \(2 \times 30^\circ\):
\[ 2 \times 30^\circ = 60^\circ \]
Now substitute this back into the deviation formula:
\[ \Delta = 180^\circ - 60^\circ = 120^\circ \]

6. **Conclusion**:
The deviation produced by the mirror is \(120^\circ\).

### Final Answer:
The deviation produced by the mirror is \(120^\circ\).