Question

Define power of lens? What is its unit!?One student uses of a lens of focal length 50cm and another of -50cm. What is the nature of the lens and its power used by each of them?

Answer 1

power is defined as the degree of convergence or divergence of ray of light by a lens .
Its SI unit is Dioptre
p= 1/f
1/50
0.02 dioptre (it is a convex lens )
p= 1/f
1/-50
=-0.02( it is a concave lens)
hope it helps....