Can your microwave oven really measure the speed of light? Yes, it can be done. And since many of the suggested experiments also involve chocolate, it will be done. Oh yes, it will be done.
First, a brief summary of the facts:
Microwaves are part of the electromagnetic spectrum. The electromagnetic spectrum includes radio waves, infrared waves, visible light, and ultraviolet, and can best be described as a bunch of things that behave the way visible light does, even though we can't see them, which is a shame, since that would eliminate the need for recreational drugs. Microwaves move at the same speed that light does.
Microwave ovens produce microwaves in a special configuration, called a standing wave. A standing wave. A standing wave is a wave that so perfectly fits its container that it looks like it looks like it's standing still. Most people have created standing waves as children playing with jump ropes. If you lift and push at just the right times, the jump rope will have one place that moves into peaks and valleys, while staying still at the two ends. If you put a little more effort into it, you can make the jump rope have two places that form peaks and valleys, and three points where it seems to be holding still.
This s-like curve is one wave, and the length of it is one wavelength. (Yes, I know that that's obvious. Just bring that up whenever people complain that physics is hard.)
Inside the microwave, the peaks and valleys of a standing wave translate to big time oscillation, and that oscillation cooks the food. The nodes, or places where the jump rope seems to stand still, translate to no oscillation.
That's why the microwave tray rotates. It has to move the food in order to make sure that every part of your frozen dinner is exposed to the places of highest oscillation. If it just stayed still, the peas would be roughly at the temperature of the center of the sun, and be little green time bombs waiting to nuke your tongue, while the tater tots would be frozen, ready to break your teeth when you bite into it. Because frozen foods hate us as much as we hate them. It's inarguable. That's why I put it in the ‘facts' section.
The number of waves that blow by a certain point per second is said to be the frequency of the waves. The frequency, the wavelengths, and the speed of waves have been established as having a set relationship with one another.
(Frequency) x (Wavelength) = Speed
This makes sense both logically and experimentally. For example, if you were sitting on the side of a one mile loop trail, and a runner ran past you once every ten minutes, you could determine their speed like this:
(6 loops per hour) X (1 mile per loop) = A speed of six miles per hour.
If six full waves cycled past you in one hour, the speed would be the same.
And so, we are armed with all the theoretical knowledge we need. Into the fray!
Every site I've been to agrees that you'll need a metric ruler and a microwave with the product label still attached, but the rotating tray brutally ripped out. They disagree, however, on the proper experimental material to nuke. Some sites say you'll need whipped egg whites on a plate. Others favor marshmallows in a dish. I'm going to recommend you go with the ones that recommend either wide chocolate bars or a layer of chocolate chips over a tray. Unless you can find chocolate marshmallows.
The brandy snifter is optional.
Whatever sacrificial material you use – put it in the microwave and nuke it. Keep an eye on it as it cooks, and take it out just as you see spots on it start to melt.
Since the tray isn't moving, it won't melt evenly. Certain points will have begun to bubble and smoke while leaving the rest of the food unharmed and undeservedly smug. Use the ruler to measure the distance between those two points. That is half the wavelength of the microwaves that the oven produces.
(Melty-bits shown in red.)
Double that distance, and you'll have the wavelength of the waves emitted by the microwave.
This is the tough part. I kept it from you until now because I didn't want you to bail on your education. The information of label on most microwaves is on the back. Yes, I know that's where the spiders and rotting pieces of tuna are, but you have only yourself to blame. You should have cleaned more regularly.
On the label, there will be information as to what frequency the microwave emits waves at. After that, it's simple.
(Frequency) x (Wavelength) = Speed of Light.
And then you get to eat the chocolate.