Question

the focal length of concave lens is 40 cm its power is​

Answer 1

Answer:

Given, focal length of convex lens (f)

= + 40 cm = + 0.4 m

Power of lens = 1/f (in meter)

= 1/ (+ 0.4) m

= + 2.5 D

So, Power of convex lens is + 2.5 D.

Explanation:

Answer 2

The focal length of a concave lens is equal to -2.5 D

Explanation:

• this is because the focal length of a concave lens is always negative. The the power is the inverse of the focal length of a lens. For this case we have to take the focal length in terms of metre. Hence in the above case it is given that the focal length is 40cm or 0.4m
• So the power =- 1/0.4= -2.5D the sign is used to determine the type of lens used

To know more,

this is the science that studies the physiographic units such as ..

.https://brainly.in/question/22161112