The mirror used in search lights is

Options

A. concave
B. convex
C. plane
D. none of these

Answer

To determine the type of mirror used in searchlights, we need to analyze the requirements for effective light projection.

### Step-by-Step Solution:

1. **Understanding the Requirements of a Searchlight**:
- A searchlight needs to emit a concentrated beam of light that travels far distances. This means the light beam should be parallel and not diverging.

2. **Identifying Mirror Types**:
- There are three main types of mirrors to consider: concave mirrors, convex mirrors, and plane mirrors.

3. **Analyzing the Concave Mirror**:
- A concave mirror can focus light. When a light source is placed at its focal point, the light rays reflect off the mirror and travel parallel to each other. This is ideal for a searchlight as it allows the light to travel long distances without spreading out.

4. **Analyzing the Convex Mirror**:
- A convex mirror, on the other hand, diverges light rays. If a light source is placed in front of a convex mirror, the rays will spread out, making it unsuitable for a searchlight since it cannot project a focused beam.

5. **Analyzing the Plane Mirror**:
- A plane mirror also does not focus light. Light rays reflecting off a plane mirror will also diverge, which means it cannot be used effectively in a searchlight.

6. **Conclusion**:
- Based on the analysis, the only type of mirror that can produce a parallel beam of light when a light source is placed at its focal point is the **concave mirror**. Therefore, the correct answer to the question is that the mirror used in searchlights is a **concave mirror**.