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
