Question

The focal length of a convex lens of power 4 D is

Answer 1

Answer:

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

Explanation:

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

Answer 2

$\huge{\underline{\tt{\red{Answer-}}}}$25cm

$\small{\underline{\tt{\blue{Given-}}}}$the power of a lens is 4 dioptre.

$\small{\underline{\tt{\blue{Find-}}}}$Focal length=>$\boxed{Power = \frac{1}{Focal \ length} }$

$\Rightarrow \frac{1}{4}cm= 25cm$