NCERT Question 4 (MCQ) - Chapter 10 Class 10 - Light - Reflection and Refraction

A spherical mirror and a thin spherical lens have each a focal length of –15cm. The mirror and the lens are likely to be

(a) both concave.

(b) both convex.

Answer

(a) both concave.

Explanation

For mirror, 

Concave mirror has its focus on the left.

So, focal length of concave mirror is negative

For lens,

We take focal length of concave lens as negative

Thus, focal length of both Concave mirror and Concave Lens is negative