Question

Relate power and focal length. find the power of the lens whose focal length is 25cm.

Answer 1

Answer:

4D

Explanation:

Power of the lens is always the reciprocal of the focal length of the lens.

Focal length of the lens = f = 25 cm = 0.25 m

So, power of the lens = 1 / f

P = 1 / 0.25 

P = 4 D

Since power of a lens is positive which shows that, the lens is a converging lens.

Hopefully it helps.

Thanks

Answer 2

Power is defined as the reciprocal of its focal length. It is denoted by letter D which stands for dioptre.

That is p=1/f

Now , it is given that f = 25cm

So p = 1/25

= 0.4D