Question

How are power and focal length of a lens related? You are provided with two lenses of focal length 20 cm and 40 cm respectively. Which lens will you use to obtain more convergent light?

Answer 1

Power of a lens is inversely proportional to its focal length therefore lens having focal length of 20 cm will provide more convergence.

Answer 2

The power of a lens is related to its focal length as

P = \(\frac{1}{f}\)(in m)

More the power of a lens more is its converging power. Thus, the lens of shorter focal length will have more converging power.