Question

State the nature of the lens
and the focal length if its
power is +4D.​

Answer 1

Answer and Explanation:

The focal length is 0.25m = 25cm

We know that,

$\boxed{Power = \frac{1}{Focal \ length} }$

+4D = 1 / Focal Length

Focal length = 1/4

Focal length = 0.25 m = 25cm

Since, focal length is positive the lens will be of converging type

Therefore,

The given lens is a converging lens with 0.25m or 25cm focal length