Final answer:
The distance a wave has to propagate in a medium with a skin depth of 0.1 m, so that the amplitude attenuates by 20 dB, is 0.05 m.
Step-by-step explanation:
The skin depth of a medium is a measure of the distance that a wave's amplitude decreases by a certain amount. In this case, the skin depth is 0.1 m and the wave attenuates by 20 dB. To find the distance that the wave has to propagate, we can use the formula:
d = skin depth / (10 * attenuation in dB)
Plugging in the values, we get:
d = 0.1 m / (10 * 20 dB) = 0.0005 m = 0.05 m
Therefore, the distance that the wave has to propagate is 0.05 m, so the correct answer is b. 0.05.