Wave Theory

Christian Huygens (1678) proposed the wave theory: light is a disturbance from a source, travelling as a longitudinal mechanical wave through a hypothetical medium called ether, presumed to fill all space (since a mechanical wave requires a medium to propagate through). This theory successfully explained reflection, refraction, interference and diffraction. But once the existence of ether was later shown to be false, the theory could no longer explain how light propagates through the vacuum of space; and because it modelled light as a *longi …