What is "chromatic aberration"

Aberration \Ab`er*ra"tion\, n. [L. aberratio: cf. F. aberration. See Aberrate.]

1. The act of wandering; deviation, especially from truth or moral rectitude, from the natural state, or from a type. ``The aberration of youth.''
   --Hall. ``Aberrations from theory.''
   --Burke.

2. A partial alienation of reason. ``Occasional aberrations of intellect.''
   --Lingard.

   Whims, which at first are the aberrations of a single brain, pass with heat into epidemic form.
   --I. Taylor.

3. (Astron.) A small periodical change of position in the stars and other heavenly bodies, due to the combined effect of the motion of light and the motion of the observer; called annual aberration, when the observer's motion is that of the earth in its orbit, and daily or diurnal aberration, when of the earth on its axis; amounting when greatest, in the former case, to 20.4'', and in the latter, to 0.3''. Planetary aberration is that due to the motion of light and the motion of the planet relative to the earth.

4. (Opt.) The convergence to different foci, by a lens or mirror, of rays of light emanating from one and the same point, or the deviation of such rays from a single focus; called spherical aberration, when due to the spherical form of the lens or mirror, such form giving different foci for central and marginal rays; and chromatic aberration, when due to different refrangibilities of the colored rays of the spectrum, those of each color having a distinct focus.

5. (Physiol.) The passage of blood or other fluid into parts not appropriate for it.

6. (Law) The producing of an unintended effect by the glancing of an instrument, as when a shot intended for A glances and strikes B.

   Syn: Insanity; lunacy; madness; derangement; alienation; mania; dementia; hallucination; illusion; delusion. See Insanity.

n. (context optics English) An optical aberration, in which an image has coloured fringes, caused by differential refraction of light of different wavelengths.

n. an optical aberration in which the image has colored fringes

In optics, chromatic aberration (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.

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.