Measuring the Speed of Light in Butter

Public summary: 

Measure the speed of light using butter and a microwave!

Measure the speed of light
Useful information
Kit List: 

Butter/Margarine/Cheap Spread

Packing Away: 

The microwave lives randomly in the cupboard, rulers in the stationary box and everything else is disposable

Frequency of use: 

Explain how light is a wave and that microwaves are just some wavelength of this. A microwave has a generator, the nodes and antinodes have different energy levels, the rotation means food gets heated evenly. (aninodes max heat, nodes have no heating bar diffusion)
Remove the turntable from the microwave, this allows us to identify the hotspots. To do so take some cardboard/paper plate and spread a fine layer of spread evenly across it. Place in the microwave for a few seconds. You should notice a pattern in the melted butter, if not keep microwaving it until you see things.
Use the ruler to measure the distance between the hotspots. this gives us half the wavelength of microwaves.
Then speed of light = wavelength * frequency. The frequency of microwaves is around 2.5Ghz.
The speed of light is 29,979,245,800 cm/sec (as you'll probably measure the distance in cm)
For thought how can you improve the accuracy? Choose some other em wave, better generator, deal with reflection inside the microwave.

Risk Assessment
Risk Assessment: 

don't put foil in the microwave
don't touch the butter while warm
dont put children in microwave