Undulatory

[Sarah]

Moving in the manner of undulations, or waves; resembling themotion of waves, which successively rise or swell rise or swell andfall; pertaining to a propagated alternating motion, similar to thatof waves. Undulatory theory, or Wave theory (of light) (Opt.), thattheory which regards its various phenomena as due to undulations inan ethereal medium, propagated from the radiant with immense, butmeasurable, velocities, and producing different impressions on theretina according to their amplitude and frequency, the sensation ofbrightness depending on the former, that of color on the latter. Theundulations are supposed to take place, not in the direction ofpropagation, as in the air waves constituting sound, buttransversely, and the various phenomena of refraction, polarization,interference, etc., are attributable to the different affections ofthese undulations in different circumstances of propagation. It iscomputed that the frequency of the undulations corresponding to theseveral colors of the spectrum ranges from 458 millions of millionsper second for the extreme red ray, to 727 millions of millions forthe extreme violet, and their lengths for the same colors, from thethirty-eight thousandth to the sixty thousandth part of an inch. Thetheory of ethereal undulations is applicable not only to thephenomena of light, but also to those of heat.