Huygens' principle

== English == === Etymology === From Christiaan Huygens, Dutch physicist. === Proper noun === Huygens' principle (physics) The assumption that each point on a wavefront may be regarded as a source of secondary waves and that the position of the wavefront at a later time is determined by the envelope of these secondary waves; proposed in order to explain the fact that light travels in a straight line and casts sharp shadows. ==== Related terms ==== Huygens-Fresnel principle