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?

The power of lens is inversely proportional to the focal length of the lens and the lens with focal length 20 has more power when compared to a lens with a focal length of 40 cm. The lens having higher power is used to produce more convergent light.