Which mirror is used :
as a rear-view mirror in vehicles ?

Options

A. Convex mirrors
B. Concave mirrors
C. Plane mirrors
D. Both A and B

Answer

### Step-by-Step Solution:

1. **Identify the Types of Mirrors**:
- There are three main types of mirrors: concave, convex, and plain mirrors.

2. **Understand the Function of Rear-View Mirrors**:
- Rear-view mirrors are used in vehicles to provide a view of the area behind the vehicle. This requires a mirror that can show a wide field of view.

3. **Consider the Properties of Concave and Convex Mirrors**:
- Concave mirrors can magnify images, but they have a limited field of view and can create real images that may not be practical for rear-view purposes.
- Convex mirrors, on the other hand, always produce virtual images that are smaller than the object but provide a wider field of view.

4. **Determine the Best Option**:
- Since rear-view mirrors need to show a larger area behind the vehicle, convex mirrors are preferred. They allow drivers to see more of the road and any vehicles approaching from behind.

5. **Conclusion**:
- Therefore, the type of mirror used as a rear-view mirror in vehicles is a **convex mirror**.