Question

The radius of curvature of a concave mirror of focal length 20 cm is:

• A. 15 cm
• B. 10 cm
• C. 40 cm
• D. 60 cm

Hint:

For any spherical mirror, the radius of curvature (\( R \)) is always twice the focal length (\( f \)), i.e., \( R = 2f \).

Answer 1

The Correct Option is C

Step 1: Understanding the relationship between focal length and radius of curvature. The radius of curvature (\( R \)) and the focal length (\( f \)) of a concave mirror are related by: \[ R = 2f \]
Step 2: Calculating the radius of curvature. Given \( f = 20 \) cm, \[ R = 2 \times 20 = 40 \text{ cm} \]
Step 3: Explanation of incorrect options.
- 15 cm, 10 cm, 60 cm are incorrect as they do not follow the formula \( R = 2f \).