Question

What is meant by power of lens write its si unit a student uses a lens of focal length 40cm and another one of - 20cm write the nature and power of each lens?

Answer 1

Power of a lens is reciprocal of its focal length. It's si unit is diaptor

Power =100/focal length (in cm)

P=100/40

=2.5 diaptor

P=100/20

=5 diaptor