Question

What is chromatic aberration? Derive the conditions for the achromatism when two lenses a
(i) in contact and (ii) separated by a distance​

Answer 1

Answer:

chromatic aberration (abbreviated CA; also called chromatic distortion and spherochromatism) is a failure of a lens to focus all colors to the same point.[1] It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent materials decreases with increasing wavelength.[2] Since the focal length of a lens depends on the refractive index, this variation in refractive index affects focusing.[3] Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image.