00:01
All right, here we've been told the frequencies of different wavelengths and of different electromagnetic waves, and we want to find their difference in wavelength.
00:12
So for all electromagnetic waves, the speed of the wave is going to be equal to the waves ' wavelength times its frequency.
00:22
So if we want to find the wavelength of a wave, you know that the wavelength is equal to the speed divided by the frequency.
00:31
Okay? if we want to know the difference in wavelengths, w1, wavelength 1 minus wavelength 2, we also can call this lambda 1 minus lambda 2, it's going to be equal to c over f1 minus c over f2.
00:50
The speed of electromagnetic radiation is always the same, but the frequencies and the wavelengths can be different.
00:58
Okay, this is the same thing as c times 1 over f1 minus 1 over f.
01:12
Okay, so this is 3, this is 3 times 10 to the 8th meters per second times for part a, frequency 1 is 50 kilohertz, so this is 1 over 5.
01:32
0 times 10 to the 3 hertz.
01:37
So this is in seconds, 1 over seconds is seconds, minus 1 over 52 times 10 to the 3 hertz.
01:51
Hertz is 1 over seconds, 1 over seconds, 1 over seconds.
01:55
I know units get kind of crazy sometimes.
01:58
So the answer to part a is 1 over 50 to the 3.
02:04
50 times 10 to the 3, so 1 over 5 times 10 to the 4th, minus 1 over 5 .2 times 10 to the 4th, times 3 times 10 to the 8th.
02:22
So this is going to be 230 .8 meters.
02:32
Okay, that's our answer to part a...