What is "decomposition of light"

Decomposition \De*com`po*si"tion\, n. [Pref. de- (in sense 3 intensive) + composition: cf. F. d['e]composition. Cf. Decomposition.]

1. The act or process of resolving the constituent parts of a compound body or substance into its elementary parts; separation into constituent part; analysis; the decay or dissolution consequent on the removal or alteration of some of the ingredients of a compound; disintegration; as, the decomposition of wood, rocks, etc.

2. The state of being reduced into original elements.

3. Repeated composition; a combination of compounds. [Obs.]

   Decomposition of forces. Same as Resolution of forces, under Resolution.

   Decomposition of light, the division of light into the prismatic colors.