work out the speed of light by making cheese on toast.

source: http://www.youtube.com/watch?v=_t0EgviIbR0

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41:04 - Dara O'Briain works out the speed of light by making cheese on toast.

A microwave travels at the speed of light.

speed of light = frequency x wavelength

6.5cm between hot spots of cheese x 2 = wavelength = 13cm = 0.13metres

frequency (from back of microwave) = 2450 MHz = 2.45 x 109 giga hertz
calculated speed of light = 0.13m x 2.45 x109 = 3.2 x 108 m/s

Actual speed of light is 3.0 x 108 m/s (300,000 km/s=3 x 105 km/s)

Pretty close, eh!