Why mirror does not have power?

Power is defined for lenses since there the light rays are travelling from one medium to another and the deviation or the behavior of light depends on the power of a lens but incase of mirror since the rays are dealing in one medium only [reflection] so there is no sense of defining power for mirror so thats why we don't use this term for mirrors. 

  • 1

In a plane mirror, the radius of curvature is infinitly long, so the focus will be at infinity. Another way to say it is that a plane mirror has no curvature, and as curvature becomes increasingly small, focal length becomes increasingly long. At a curvature of zero, focal length becomes infinite. 

Focal length(f) is given by f=R/2 where R is radius of curvature.. 
Once again, it's infinity!

now power is 1/f ..therefore in a plane mirror it will be 1/infinity = 0

hence no power !

hope it answers your question

  • 0
What are you looking for?