Question

What is meant by power of lens write its si unit A student uses a lens of focal lenght 40cm and another of -20 cm write the nature and power of each lens

Answer 1

The ability of the lens to converge the rays of light falling on it, is called power of lens.
SI unit= dioptre
First lens used by student is convex and the second is concave.
Power of first lens= 2.5dioptre & that of second= - 5 dioptre