How does 5 msec = 250 Hz?

5 times 50 equals 250, come on now.

>>8044945
why do we multiply by 50?

>>8044945
is it because 5 msec = 10^1?

wat

>>8044930
5 squared is 25, then converting from ms to seconds, then hz adds a zero.

>>8044930
It doesn't, nor does the diagram imply that.

Also the bottom obviously isn't the Fourier decomposition of the top because the beat frequency in the top is ~140 Hz whereas the difference on the bottom is much larger.

I hope the exam for whatever you are studying this for isn't tomorrow.

>>8044959
Also the fact that the beats don't take the wave to zero implies that there is a third frequency present, maybe more.

But it may be that the diagram was just intended to be illustrative and not much thought was put into it.

>>8044987
>don't take the wave to zero
Never mind, it should go to zero if they're equal in amplitude. I think the upper diagram might be consistent with two frequencies with the lower frequency having a larger amplitude.

>>8044959
how do you determine the beat frequency from a time domain graph like OPs?

How to get the frequency from a time domain graph?

>>8045011
By looking at the period with which it fluctuates back and forth between high amplitude from constructive interference and low amplitude from destructive interference. That's what beats are. In the diagram, that period is about 7 msec.

File: plot.png (6KB, 640x480px) Image search: [Google]

6KB, 640x480px

>>8044995
>I think the upper diagram might be consistent with two frequencies with the lower frequency having a larger amplitude.
Looks like it is.

>>8045042
Which means the only thing wrong with the bottom plot is the x-axis, which is out of whack by a factor of ~2.3.

>>8044930
[math]\displaystyle 5ms = \frac{5s}{1000} = \frac{1s}{200} [/math]
[math]\displaystyle (\frac{1s}{200})^{-1} = 200 Hz[/math]