Assertion (A): The focal length of the convex  mirror will increase, if the mirror is placed in  water.  

Reason (R): The focal length of a convex mirror of  radius R is equal to, f =  R/2  .  

Answer  

Here,

  • Focal length of the spherical mirror  does not depend on the medium in which it is  placed. 
    Thus, focal length of convex mirror will remain the same.

  • For spherical mirrors, Focal length = (Radius of Curvature/2) 

 

mirrors-as-a-part-of-sphere---teachoo.jpg

 

Thus,

  • Assertion is false
  • Reasoning is true

 

So, the correct answer is (d) 

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CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo