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
- both concave
- both convex
- the mirror is concave and the lens is convex
- the mirror is convex, but the lens is concave.
The Correct Option is A
Solution and Explanation
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.
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Concepts Used:
Spherical Mirrors
A spherical mirror is a mirror which has been cut out of a spherical surface.
There are two kinds of spherical mirrors:
- Convex Mirror
- Concave Mirror
Concave Mirror
Concave mirrors are also called converging mirrors, because in these types of mirrors, light rays converge at a point after impact and reflect back from the reflective surface of the mirror.
Convex Mirror
The convex mirror has a reflective surface that is curved outward. Regardless of the distance between the subject and the mirrors, these mirrors are "always" virtual, upright and reduced.