Question

A narrow white light beam fails to converge at a point after going through a converging lens. this defect is known as

Answer 1

it is known as Chromatic aberration. it is also called chromatic distortion and spherochromatism). It is an effect resulting from dispersion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have different refractive indices for different wavelengths of light.