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# Light Speed Challenge

I challenge you to create an experiment using household items that can tell you that light has a finite speed and share the experiment in the comments section. If possible, use elementary maths to determine an approximation of the speed of light.

Note by Sharky Kesa
4 years ago

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Inside of a microwave, you have standing waves (the microwaves) that span the interior of the box. They must have anchors at the walls and so the wavelength is generally the dimension of the microwave divided by some integer. This makes it so that some parts of the microwave oven become hotter than others. This is the reason that microwave ovens have a rotating platform is to spin food through the standing waves and try to compensate for the uneven distribution of the heating effect.

Anyways, if you take out the rotating platform then you can use the microwave as a sort of magnifying glass and burn things. Put a paper towel, or something that can sort of melt but not completely, and let it burn/melt in the microwave for a while. Eventually you'll see that there are burns at regular intervals along the material. This interval is one half the wavelength of the standing microwaves. Multiply that length by two and find the frequency of the radiation your microwave produces, hopefully printed inside the door. From that you can find that the speed of light is finite because both the frequency and the wavelength are finite, i.e. $$c = \lambda f$$

Staff - 4 years ago

Why don't I look up in an encyclopedia to find out the frequency of, say, sodium vapor light, and then use simple interferometry setups to determine its wavelength, from which I can compute its speed? Early scientists from the Greek times have tried to find ways to measure its speed, but it wasn't until Romer's observations of the moons of Jupiter in late 17th century before any reasonable estimate of it could be had. Newton and others were able to determine its wavelength much more readily than its frequency (and therefore speed). So, for this poser to be a fair one, we shouldn't be allowed to know the frequency of light in advance. Let me think on it and see if there's a way to do it that can be done by a home experimenter, without that information.

- 3 years, 11 months ago

There are 2 ways to do that.. They're simple and not new.. Search in Google about the following ways *1 counting light speed with mirrors - Michelson. *2 counting light spead with gearwheel - Fizeau.

I hope you will find what you are looking for

- 4 years ago

Could you tell us what happens in the experiment?

- 4 years ago