00:01
Okay, so we're doing chapter 32, problem 22.
00:04
So they want us to use ray diagrams to show that the mirror equation is valid for a convex mirror, as long as we take the focal length to be considered negative.
00:15
So we want to show this geometrically and derive this mirror equation.
00:22
So let's start out by drawing our ray diagram here.
00:26
So this will be our plane, and then we'll make the mirror here.
00:33
Let's call this our focal links.
00:36
And let's get to get it out a bit.
00:38
And this can be our radius of curvature.
00:43
So let's put an object here.
00:48
And this is at a distance d .0.
00:50
We consider our object distance.
00:54
So let's figure out where the image will be formed by doing our ray tracing rules.
01:09
So first one will be coming in parallel.
01:12
And it'll bounce back like it came through the focal lens.
01:15
Like that.
01:19
The next one is going to go straight through like it was hitting the radius of curvature.
01:31
So it's all the way like that and it'll bounce straight backwards.
01:35
The next one is going to bounce an in right on the axis and bounce back like a plane here.
01:46
So if we trace these back, we should see that we're left with a little image right here.
01:54
So now, now we want to figure out if we can derive what this image distance is.
02:02
So let's draw some angles here.
02:04
First, we know this is theta and this is data because this is just plain mirror interaction, which is angle of reflection equals angle of incidence.
02:16
The other angle we can describe here is this is also theta.
02:21
We can also say this angle, as alpha.
02:36
So from that, we call this the object height, h -s -not, and h -i will be the image height.
02:45
So we can now use our angles and some trigonometry to define some factors.
02:50
So looking at this small triangle here, we can say the tangent of theta is the opposite over the adjacent.
02:59
So the the opposite is h -i and bottom is negative d -i because we know the image distance is negative that's on the other side of the view.
03:15
This is also equal to if we look at this triangle, using this, the tangent of theta is also equal to the object height over the object instance...