Question
Science Question on Spherical Mirrors
A spherical mirror and a thin spherical lens have each a focal length of −15 cm. The mirror and the lens are likely to be
A
both concave
B
both convex
C
the mirror is concave and the lens is convex
D
the mirror is convex, but the lens is concave.
Answer
both concave
Explanation
Solution
By convention, the focal length of a concave mirror and a concave lens are taken as negative. Hence, both the spherical mirror and the thin spherical lens are concave in nature.
So, the correct option is (A): both concave.