A spherical mirror and a thin spherical lens both have focal length -20 cm. Which is true?

Question

A spherical mirror and a thin spherical lens both have focal length -20 cm. Which is true? — Exam MCQ

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D. Both are concave — With Cartesian signs, both a concave mirror and a concave lens have negative focal lengths.

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A. Both are convex

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B. The mirror is concave and the lens is convex

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C. The mirror is convex and the lens is concave