Michelson Interferometer (2D)

Move a mirror, tilt it, change the colour and the coherence, and count fringes to measure a wavelength.

Live readout

Numerical checks

The science

The two beams differ by 2 d cos(alpha) (alpha = angle of the ray, d = arm-length difference) plus a wedge term 2 (tilt . position) for a tilted mirror. The detector sees I = (1 + V cos(2 pi delta / lambda)) / 2. Moving a mirror by Dd sweeps N = 2 Dd / lambda fringes, so lambda = 2 Dd / N.

Visibility uses a Gaussian coherence envelope V = exp(-(2d / lc)^2), a simplification of a real source spectrum.
The image mixes angle and pupil coordinates in one picture for clarity; real fringe patterns need a collimated, aligned instrument.

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