<Tr> <Td> Defocus <P> Tilt Spherical aberration Astigmatism Coma Distortion Petzval field curvature Chromatic aberration </P> </Td> </Tr> <P> Tilt Spherical aberration Astigmatism Coma Distortion Petzval field curvature Chromatic aberration </P> <P> In optics, chromatic aberration (abbreviated CA; also called chromatic distortion and spherochromatism) 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 . The refractive index of transparent materials decreases with increasing wavelength in degrees unique to each . </P> <P> Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point . Since the focal length f of a lens is dependent on the refractive index n, different wavelengths of light will be focused on different positions . </P>

4. the chromatic aberration in lenses is due to the