00:01
Okay, so we're doing chapter 32 problem six.
00:04
So this problem says suppose you are 88 centimeters from a plain mirror.
00:10
What area of the mirror is used to reflect the rays entering one eye from a point on the tip of your nose if your pupil diameter is 4 .5 millimeters.
00:20
Okay, so we'll do diameter for the pupil pupil is 4 .5 millimeters.
00:30
So let's draw out of eye.
00:32
Out here very poorly.
00:37
I've got a little pupil here.
00:41
So now we know that this is d pupil.
00:47
And this is our plain mirror, which is the distance 8, 7 meters away.
00:56
So how plain mirrors work is that the image is always the same distance away as the object.
01:05
So we know this is creating a virtual image over here.
01:09
Here also 88 centimeters away, which means this is the point where the light gets traced back to.
01:20
So if we draw straight lines from the top of the pupil back and the bottom of the pupil back, we've got a triangle here.
01:30
So now we want to find this distance of these light rays in the mirror...