Aberration, CHROMATIC

As rays of different lengths, and hence of different colors, have different refractive indices, a single converging lens is unable to bring them all to a focus at a single point. This phenomenon is known as chromatic aberration. Thus the image of an object formed by a lens and projected on a screen is surrounded by a colored border, the color depending upon the distance from the screen to the lens. Aberration, CONSTANT OF. Term applied to ratio of earth's velocity to velocity of light. 20."445 is value commonly used in astronomical computations. Recent determinations give a somewhat larger value, about 20."50.