Question

What is meant by power of a lens ? Write its SI unit. A student uses a lens of focal length 40 cm and another of –20 cm. Write the nature and power of each lens

Answer 1

power of a lens is reciprocal of focal length

SI unit of power is diaptore

when focal length is 40cm power is, 1/40 cm =0.25

nature of alens is virtual errect

when focal length is-20cm the power is 1/20=.05

nature is real inverted