Question

the power of a convex lens of focal length 25 is? ​

Answer 1

Power of a convex lens is defined as its capability to converge light rays. The shorter the focal length, the higher its power will be and vice-versa. This means that power is inversely proportional to the focal length (in meters) of the lens.

In this question, if the focal length is not in meters, it needs to be converted to meters.

For example, if it is 25 cm, it can be converted to meters by dividing by 100.

F = + 25/100 = +0.25 m

The power of a lens is calculated by the formula P = 1/F

So, power = 1/0.25 = 1/25/100 = 1/1/4 = 4 D

If we assume that the focal length is in meters already, then the power is

1/25 = 4/100 = 0.04 D