Question

Explain power of combination & definition of power of lens ?

Answer 1

Power of a lens is defined as the reciprocal of focal-length. Its SI unit is Diopter (D), which is actually reciprocal of 1 meter.

Power of lens=1/Focal length( in metres)

The term power of combination is used when two or more thin lenses are closed together,then the optical power of the combined lenses is approximately equal to the sum of the optical powers of each lens: P = P₁ + P₂.