00:01
Number 83, it's about a wave on a string, and the wave is moving to the right, and we're asked to describe the direction to each one of these points on the wave is moving.
00:12
Remember, this is a transverse wave.
00:16
The particles of the medium, like if i looked at this piece of the string, it's just going to go up to there, then down to here, then up to there, and down to there, and up to there.
00:24
So the direction of the particle is perpendicular to the direction of the wave.
00:30
So focus and look at, let's look at point b here while the wave moves through it.
00:35
So i'm going to move this wave through it.
00:40
So watch as this wave moves to the right, what particle b would go.
00:43
So i'm going straight up.
00:45
You can tell b would be going straight up.
00:48
And now b would be at the highest point.
00:50
And b would start coming down.
00:53
Okay.
00:54
So at this position, at t equals zero, b would be moving up.
01:04
And the same thing with c.
01:07
C would be moving up.
01:09
Now, a would be at the point where it's changing directions...