00:01
Here i'll review how it is that we see an image, an optical image.
00:09
And there are two different light processes that can create images.
00:14
They're known as reflection.
00:16
There's another one called refraction that happens in lenses, whereas reflection happens in mirrors.
00:24
And what those mirrors do is they will take light and redirect light.
00:32
So when your brain, when you get in front of that light and see it, your brain believes the light came straight from the source.
00:43
When in reality, it took a little bit of a turn due to the physical process going on.
00:50
So there are two things that you need to see an image through reflection.
00:56
So first of all, there has to be a source getting reflected.
01:03
Off of a surface like a mirror, but also that reflected light has to get into your eye, because your brain is part of this whole image thing.
01:37
So it could just get into one eye or both eyes.
01:41
It really doesn't matter.
01:43
So oftentimes when we show figures with image formation, we forget about the fact that there has to be an observer to see that image.
01:53
I mean, the image is still there, but for you to describe it.
01:58
And let's see that.
02:00
It's there.
02:02
The light has to get into your eye.
02:04
So let's take an example.
02:07
Let's have person a, i don't know what to call them, ann, is going to shine a light onto a mirror on a table towards bill.
02:19
We're just going to use a and b, simple names.
02:23
What reflection is from a mirror, is it's a law that says that the angle of reflection has to equal the angle of incidence.
02:34
So here comes the ray of light onto the mirror.
02:37
It's going to hit that mirror and bounce back at the same angle it came in on, and usually you measure that angle with respect to a normal to the surface.
02:49
So here i'll show theta n, or theta a, and a theta b.
03:01
So if bill is going to see the image of that flashlight, their eye had better be right in the way of that light.
03:12
So there's their eye.
03:13
Let's make them a blue -eyed person or green -eyed or something.
03:16
Purple -eyed.
03:18
Okay.
03:18
So bill would see the reflected light, but anne would not.
03:24
Now, the reflection is taking place, but none of that reflected light is going towards anne's eyeball.
03:31
So bill will see the reflection because of the placement of his eye, but anne won't.
03:50
So for her, if it's a dark room, the mirror will just look like a black mirror, a dark mirror.
03:57
Now, if we draw the ray backwards, we're not going to show the entire image formation.
04:04
But bill, remember, bill is tricked by the reflection.
04:12
Bill thinks the light came straight into his eye.
04:32
And it turns out what that means is it looks like the light source is actually under the mirror, inside the mirror, you know, behind the point where it reflected.
04:45
So the image is actually back behind the.
04:49
The mirror...