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If a mirror has a focal length of + 15 c...

If a mirror has a focal length of + 15 cm, it is a

A

convex mirror

B

concave mirror

C

plane mirror

D

none of these

Text Solution

AI Generated Solution

The correct Answer is:
To determine the type of mirror based on its focal length, we can follow these steps: ### Step 1: Understand the Sign Convention In optics, the sign convention is crucial. For mirrors: - Focal length (f) is positive for convex mirrors. - Focal length (f) is negative for concave mirrors. - Plane mirrors have an infinite focal length. ### Step 2: Analyze the Given Focal Length The problem states that the focal length of the mirror is +15 cm. According to the sign convention: - A positive focal length indicates that the mirror is either a convex mirror or a plane mirror. ### Step 3: Evaluate the Options 1. **Convex Mirror**: A convex mirror has a positive focal length. Therefore, it is a valid option. 2. **Concave Mirror**: A concave mirror has a negative focal length. Since the given focal length is positive, this option is incorrect. 3. **Plane Mirror**: A plane mirror has an infinite focal length. Since +15 cm is not infinite, this option is also incorrect. 4. **None of These**: Since we have already identified a correct option (convex mirror), this option is incorrect. ### Conclusion Based on the analysis, if a mirror has a focal length of +15 cm, it is a **convex mirror**. ---
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