Define power of lens. Derive the formula for the effective power of
lenses in contact
power of two this

The power of a lens is defined as the reciprocal of the focal length. ... Converging (convex ) lenses have positive focal lengths, so they also have positive power values. Diverging (concave ) lenses have negative focal lengths, so they also have negative power values.

d. platinum would have the greatest temperature increase because it has the lowest specific heat.