An electromagnetic wave, which has the frequency of f = 5MHz, goes from an unpermeable location, which has a permittivity of e = 2, to vacuum. Calculate the change in length of the wave.
NOTE: I haven't found greek letters in the post menu, so if they're somewhere in there tell me! I could fix the post then.
The Attempt at a Solution
Okay my first approach would be to calculate the length of the wave in vacuum, so: (mainly because it's easier)
L1 = c * T;
T = 1 / f
L1 = c / f
L1 = 3 * 108 / 5 * 106 = 60 m
Then i would calculate the length of the wave in the previous location (the unpermeable one):
L2 = v / f
For electromagnetic waves (if i recall correctly) we can use this formula to calculate their speed:
v = 1 / sqrt e * µ (where e is the permittivity and µ is permeability of the area)
Here's where my guess comes in. I guess that unpermeable areas do not have any permeability? So it would mean:
v = 1 / sqrt e
But then the length of the wave would be insanely small. I know that waves should be short, but the difference should clearly be bigger.
Am i wrong or right?