Radius of curvature of a concave mirror is 25 cm. What is its focal length?

Explanation

To find the focal length of a concave mirror when the radius of curvature is given, we can use the following steps:

### Step-by-Step Solution:

1. **Understand the Relationship**: The focal length (f) of a concave mirror is related to its radius of curvature (R) by the formula:
\[ f = \frac{R}{2} \]

2. **Identify the Given Value**: In this problem, the radius of curvature (R) is given as 25 cm.

3. **Substitute the Value into the Formula**: Now, we will substitute the given radius of curvature into the formula:
\[ f = \frac{25 \, \text{cm}}{2} \]

4. **Perform the Calculation**: Now, divide 25 cm by 2:
\[ f = 12.5 \, \text{cm} \]

5. **State the Final Answer**: Therefore, the focal length of the concave mirror is:
\[ f = 12.5 \, \text{cm} \]

### Final Answer:
The focal length of the concave mirror is **12.5 cm**.

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