Question

AI 20. What is meant by power of a lens ? Write the SI unit. A student uses a lens of focal length 40 cm and
another of - 20 cm. Write the nature and power of each lens.​

Answer 1

Power of the lens is the measure of degree of convergence or divergence of light rays falling on it.

Its SI unit is dioptre (D).it is always in metre.

+40 cm.....convex lens

P = 1/f = 100/40 = 2.5D

-20 cm.....concave lens

P = 1/f = 100/-20 = -5D.

Hope it helped..

Answer 2

Answer:

the ability of the lens to converge or diverge the light rays is knows as its power. It's SI unit is "Dioptere". The first person is using convex lens and the second one is using concave lens. So the first one is having hypermetropia and second is having myopiya.