Question

A student uses a lens of focal length -30cm. What is the power and nature of this lens?

Answer 1

p=1/f(in m)

p=100/-30

p=-3.3

Answer 2

Power of lens=100/f in cms or 1/f in mts.

Given that focal length of the lens=30cms

Power of lens=100/f cms or 1/f mts.
=100/-30 cms or 1/-30 mts
=3.3