Question

Find the focal length of a lens of power (-2.0)D. What type of lens is this?

Answer 1

Given, lens of power $P=(-2.0)D$

Power, $P=\frac{1}{f}$

$f=\frac{1}{p}$

$=\frac{1}{-2}$

$f=-0.5m$

Since focal length is negative, it is concave lens.