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.



(a) both concave.



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

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  1. Class 10
  2. Chapter 10 Class 10 - Light - Reflection and Refraction

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.