Michelson-Morley experiment

[pjabraham]

Nothing to do with paper modeling. For my daughter's science fair project, we decided to recreate the famous Michelson-Morley experiment demonstrating that light is a wave as shown by an interference (fringe) pattern created when two beams of light creatively and destructively interfere with each other. Here's the setup:



Here's the project in action with all the parts labelled.



Lastly, some pictures showing the fringe pattern, especially well seen on the black screen.



Hope you enjoy the pictures as much as we enjoyed putting this project together.

Phil

[Zakopious]

Very Nice !

[CharlieC]

It has been a long time since I did any Physics but I thought the point of the Michelson-Morley experiment was to investigate whether there was an "aether drift" by measuring the speed of light in the apparatus and orienting the apparatus so the speed measurement was aligned with and at right angles to the earth's rotation. The M-M interferometer was extremely sensitive and would have detected very small aether velocities. In fact, M-M detected no difference in their measurements of the speed of light and this suggested there was no aether (medium light travelled in).

Your apparatus seems to generate pretty impressive interference patterns - I assume your using a laser as the light source.

The guy you want for the wave theory of light is Thomas Young who died about 60 years before the M-M experiment.

Charlie

[pjabraham]

Charlie, you are correct. We used the setup as designed by Michelson, but should have titled this thread "Interferometry".

We used a 5mW green diode laser (eBay), which seemed to generate better patterns than a similar red diode laser. We also ordered single surface mirrors from eBay and I found a beam splitter in an old DVD drive. The whole setup cost about $25/-.

Incidentally, we did not detect any aether either!

Phil

[SCEtoAUX]

No aether either? Take a breather.

How was the look of discovery on your daughter's face when those patterns showed up?

[pjabraham]

We took a video showing the interference patterns change as the two beams of light converged or diverged. In it, you can clearly hear her say, "That's so cool!" When a fourteen year old girl says that about anything other than her cell phone, you know you've done something right. If I can, I'll try putting up a GIF sometime.

Phil