Chromatic aberration refers to the failure of a lenses to focus all the wavelengths or colours in white light at the same point. This is due to dispersion of light in glass. The refractive index of the lenses elements varies with different wavelengths of light. The different colours of white light will travel at different speeds through the lens hence they cannot all be focused at the same point. Dispersion results from the refraction of the various wavelengths of light to varying degrees.
