Question

power of a lens is 0.4 D. what is its focal lenght

Answer 1

Focal length = 1/power

F= 1/0.4 m or 100/0.4 cm

=2.5m or 250cm

Answer 2

Hey there!

Given,

Power of lens = 0.4 D

We know,

Power of lens = 1 / focal length

0.4 = 1 / f

1 / 0.4 = f

2.5 = f

or, f = 2.5 m

Hope It Helps You!