Michelson interferometer
Advanced
Precise length measurements through interference.
A beam splitter sends light along two perpendicular arms; recombining shows fringes that shift by one for each λ/2 mirror move. Used to measure tiny lengths and in LIGO.
Michelson–Morley experiment.
Needs stability to nanometres.
In more detail
A Michelson interferometer splits light into two paths, reflects them back, and recombines them to form interference fringes. Changes in path length shift the fringes, allowing very precise measurements.
Real-world uses
- The Michelson-Morley experiment searched for the aether using this device.
- Gravitational wave detectors such as LIGO are large Michelson interferometers.
- Physicists used the Michelson interferometer to test the speed of light in different frames and to measure small distances.
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Frequently asked questions
What did Michelson-Morley find?
No measurable aether wind, which supported special relativity.
Why is it so precise?
A tiny change in path length shifts fringes by a measurable amount.
Why was the Michelson–Morley experiment important?
It found no change in the speed of light with the Earth's motion, which helped lead to special relativity.
Related topics in Optics
Intensity in interference · Thin film interference · Newton's rings · Single slit diffraction · Diffraction grating · Resolving power