How do Michelson interferometers exploit interference?

Michelson interferometers exploit interference by using it to measure small distances, changes in distance, or refractive index variations.

Michelson interferometers are optical instruments that utilise the principle of interference to make precise measurements. The basic setup of a Michelson interferometer involves a beam of light being split into two paths, reflected back and then recombined to create an interference pattern. The interference pattern is created due to the wave nature of light. When the two light waves recombine, they interfere with each other. This interference can be constructive (where the waves add together to make a brighter light) or destructive (where the waves cancel each other out to make a darker light).

The key to how a Michelson interferometer exploits interference lies in the ability to precisely control the path length of one of the light beams. By moving one of the mirrors that reflect the light, the path length of one beam can be changed relative to the other. This changes the phase relationship between the two beams and thus alters the interference pattern. By observing these changes in the interference pattern, very small changes in distance can be measured. This is often used in scientific research and industry to measure things like the thickness of thin films, the flatness of optical surfaces, or tiny changes in length.

Furthermore, Michelson interferometers can also exploit interference to measure variations in the refractive index of a medium. If one of the light paths goes through a medium with a different refractive index, it will change the speed of the light and thus the phase of the light wave. This will alter the interference pattern when the light waves recombine. By observing these changes, the refractive index of the medium can be determined.

In summary, Michelson interferometers exploit the principle of interference by splitting a light beam into two paths, manipulating the path length or medium of one beam, and observing the resulting changes in the interference pattern. This allows for precise measurements of small distances, changes in distance, or refractive index variations.