Question

the power of lens is -4 find its focal length​

Answer 1

Answer:

The focal length of a diopter is1 /diopter - Strength- meters, the reciprocal of the focal length measured in meters . A 4- diopter lens brings incoming parallel rays of light to focus at 1/4 meter, it's focal length is 1/4 meter, or 250mm.

Answer 2

Answer:

If the power of the lens is -4, then its focal length​ is - 0.25 .

Explanation:

• When the subject is in focus, the focal length of the lens is the distance between the lens and the image sensor.
• The power of a lens refers to its capacity to bend the light that falls on it.
• The power of a lens is defined as the reciprocal of the focal length.

Power = 1/f (In meters)

-4 = 1/f

1/-4 = f

f = - 0.25

focal length (f) = -25

Therefore, the focal length of the lens will be -25 cm