Question

A lens has a focal length of, −10 cm. What is the power of the lens and what is its nature?

Answer 1

​Power of a lens is given by:

Power (P) = $\frac{\mathit{1}}{\mathit{f}}$

f = -10 cm​

∴​ P = $\frac{1}{10\times {10}^{-2}}$ = -10 D.

Negative sign indicates it is a diverging lens.