Question

A spherical mirror and a thin spherical lens each have a focal length of \( -15 \, \text{cm} \). The nature of the mirror and lens will be:

• A. Both concave
• B. Mirror convex and lens concave
• C. Mirror concave and lens convex
• D. Both convex

Hint:

For spherical mirrors and lenses, a negative focal length indicates a concave shape, while a positive focal length indicates a convex shape.

Answer 1

The Correct Option is A

The sign of the focal length determines the nature of the lens or mirror: - If the focal length is negative, the mirror is concave and the lens is converging (concave). - If the focal length is positive, the mirror is convex and the lens is diverging (convex). Given that both the mirror and lens have a focal length of \( -15 \, \text{cm} \), both the mirror and lens are concave.