"'C' is for chocolate! 'c' is also the symbol used for the speed of light. Defined as being 299,792,458 meters per second in vacuum, you can take a crack at measuring the ultimate speed using your microwave, a ruler and a bar of chocolate! Yum!" (Jefferson Lab - YouTube)Well, lets see how they do it:
And now the calculations:
To calculate the speed of light, we can use the math's expression of speed:
v = Dx/Dt
In this case, Dx = l and Dt = T and T = 1/f (T is the period and f the frequency of the wave, and l the wavelength).
The holes that appear in the chocolate corresponds to the maximum and minimum in a steady wave. So the wavelength is two times this distance:
l = 2 x 7.1 cm = 2 x 7.1 x 10-2 m
The frequency can be read in the back of your microwave. In this case, the value corresponds to f = 2 450 MHz = 2 450 x 106 s-1.
So, velocity is:
v = l x f <=> v= 2x(7.1 x 10-2 m) x (2 450 x 106 s-1) = 3.48 x 108 m s-1 .
That brings a percent error:
e = |c - v|/|c| x 100 = | 2.99 x 108 - 3.48 x 108|/|2.99 x 108| x 100 = 16 %
The holes that appear in the chocolate corresponds to the maximum and minimum in a steady wave. So the wavelength is two times this distance:
l = 2 x 7.1 cm = 2 x 7.1 x 10-2 m
The frequency can be read in the back of your microwave. In this case, the value corresponds to f = 2 450 MHz = 2 450 x 106 s-1.
So, velocity is:
v = l x f <=> v= 2x(7.1 x 10-2 m) x (2 450 x 106 s-1) = 3.48 x 108 m s-1 .
That brings a percent error:
e = |c - v|/|c| x 100 = | 2.99 x 108 - 3.48 x 108|/|2.99 x 108| x 100 = 16 %
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