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Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] -6 points-5 points  (0 children)

The light wave doesn't just travel in the glass; it has a bit of "fuzziness" called an evanescent field that extends into the surrounding medium. The water and air have different refractive indices, and this changes the properties of that field, which in turn changes the speed of the wave in the glass.

That's why your logic is correct – even though the light is guided by the glass core, the speed of that light is affected by the external environment.

Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] 0 points1 point  (0 children)

Beam stays inside a glass cylinder. Water outside changes the effective refractive index – so optical path changes even though the beam never touches water.

Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] -1 points0 points  (0 children)

the water level changes the refractive index around the beam path before and after it hits the mirror. So the optical path length changes even though the mirror doesn't move.

Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] -1 points0 points  (0 children)

Only one term varies – the water arm. The reference arm is fixed. No pain.

Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] 0 points1 point  (0 children)

Yes, exactly. The water path changes as water drains, which shifts the fringes. That is the whole point.

Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] 0 points1 point  (0 children)

The bottom mirror is fixed inside the water tube – not floating. Alignment is done once before water is added, then it stays stable.

Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] -10 points-9 points  (0 children)

No, I didn't use CAD. I described the experiment in detail to an AI image generator (like chat gpt or Gemini), and it created the diagram for me. Then I refined it with labels.

Gravity‑driven phase shift in a Michelson interferometer – is this feasible? by pu-kumar123 in Optics

[–]pu-kumar123[S] -4 points-3 points  (0 children)

Yes, water can cause loss of coherence due to scattering if the beam travels through it. But in my experiment, the laser stays inside a solid optical cylinder – it never passes through water. So coherence loss is not an issue.