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Question
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 ______.
Options
both concave
both convex
the mirror is concave and the lens is convex
the mirror is convex, but the lens is concave
Solution
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.
Explanation:
By convention, the focal length of a concave mirror and the focal length of a concave lens are taken as negative. Hence, both the spherical mirror and the thin spherical lens are concave in nature.
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