00:01
In problem 3132, it's an extension or variation of example 311 in the text.
00:10
It says that you are helping with a resurfacing of a primary mirror of one of the keck telescopes.
00:15
The focal length is 17 .5 meters.
00:19
The diameter of the mirror is given, but is irrelevant to the optics of the problem.
00:23
It just tells you how large the mirror is, looking at it head on.
00:27
But the curvature of the mirror is what matters.
00:29
We are looking at it 38 .6 meters away, so the person or you are standing 38 .6 meters away, we need to find the location of your image.
00:39
So we're looking for s prime.
00:41
So using the equation, 1 over f equals 1 over s plus 1 over s prime, we have 1 over 17 .5 equals 1 over 38 .6 plus 1 over s prime, which we are trying to solve.
00:57
So if you subtract the 1 over 38 .6 from both sides, add those reciprocals and then take the reciprocal of your answer.
01:05
You get almost exactly 32 meters as image distance, which means it is to the right of or in front of the mirror.
01:18
So to find the magnification, we use the equation negative si over s or the negative of the image distance over the object...