Question

What is the power of a :
convex lens
concave lens
convex mirror
concave mirror
if magnitude focal length is F
NOTE : take sign convention seriously , power is in dioptre
I just wanted to know the difference between signs in lenses and mirrors
Please tell
Thanks

Answer 1

Answer:

Power is the reciprocal of focal length in metre. It's SI unit is diopter (D)

1. Focal length of convex lens is in postive hence it's power will also be positive.

2.Focal length of concave lens is in negative hence it's power will also be negative.

3.Focal length of convex mirror is in negative hence it's power will also be negative.