Question

doctor suggests 4d lens to a patient then,find the focal length of the lens​

Answer 1

Answer:

the focal length of the lens 4D is 25cm.

Explanation:

explanation is showed in the picture.

Answer 2

Given:

Lens' power=4d

To find:

The lens' focal length

Solution:

The required focal length is 25 cm.

We have the lens power equal to 4d.

Since the lens' focal length is the reciprocal of its power, the required focal length=1/Power of the lens

We will put the power's value and obtain the focal length required.

Let the required focal length be f.

Using values, we get

f=1/Power

f=1/4

f=0.25m

On converting it, we get

f=25 cm

Therefore, the required focal length is 25 cm.