00:01
All right, what we should know to work on this problem, which is asking us if the rms value of the electric field of an electromagnetic wave is doubled, how is that going to change the rms of the magnetic field? all right, so 2 times e rms, what happens to the rms of the magnetic field? and then also how does that change the average intensity of the entire electromagnetic wave? just remember the electric field, the magnetic field are just both components of the overall electromagnetic field.
00:37
Okay.
00:38
So for one thing, the rms value of the electric field, actually let's put it this way, for an electromagnetic wave, the electric field is equal to c times the magnetic field.
00:53
Okay.
00:53
So for example, if the maximum value of e is twice as large, then the maximum value of b must also be twice as large in order for this equation.
01:02
To stay true.
01:04
Similarly, since the e rms is actually just defined for sinusoidal waves as e max over root 2, since doubling the maximum electric field doubles the maximum magnetic field, it's also true that doubling the rmse field will double the rmsb field.
01:31
So we can also say this equation works just as well.
01:35
Erms is equal to, it's equal to c times b rms.
01:48
So if we double this value, this value must also double.
01:54
So the answer to part a is two...