Back to Maxwell animations home page

Maxwell2D: Michelson interferometer, equal path lengths

Dielectric constant distribution

A Michelson interferometer was used in the famous Michelson-Morley experiment to demonstrate the non-existence of the luminiferous aether, a hypothetical medium in which light was believed to travel. In the configuration to the left, coherent light is incident on a 45° half-silvered mirror (in this case simply a thin bar with a refractive index chosen such that half the light is transmitted and half is reflected). The transmitted and reflected beams travel equal paths to ordinary mirrors (in this case simply bars with a very high refractive index), and are reflected back and recombine at the 45° mirror. This results in constructive interference for the outgoing beam to the right. If the luminiferous aether existed and the earth was moving with respect to it, then light would be expected to travel at different speeds along the two orthogonal paths, resulting in a change in the interference behaviour depending on the orientation of the instrument and the time of year. The fact that this behaviour was not observed demonstrated that this aether did not exist.
Wikipedia links: Michelson interferometer, Michelson-Morley experiment

Electric field animation

Time-averaged Poynting vector

This is an animation of the component of the electric field out of the plane of the page.The direction in which energy is travelling at any instant is proportional to the cross product of the electric and magnetic fields, known as the Poynting vector. The arrows show the direction of the Poynting vector averaged over the simulation, while the colours show its strength.