Question

Focal length of a lens is 25 cm . What is its power ?

Answer 1

See the image and ask if there is any problem.

Answer 2

Given,

Focal length of the lens = 25cm

To find,

The power of the lens.

Solution,

We can simply solve this mathematical problem by using the following mathematical process.

First of all, we have to convert the given value of focal length into si unit.

Focal length = 25cm = 0.25 metre

Now,

Power of lens = 1/focal length

Power of lens = 1/0.25 = +4 dioptre

Hence, the power of the given lens is +4D