00:02
You can really do a nice optical illusion with a concave mirror.
00:07
And by concave, it's like a shaving mirror.
00:12
So the side that's silvered upon which you look is indented inwards in a spherical way.
00:21
But the optical illusion requires putting the object at the center of curvature of the mirror, which i'm showing here.
00:30
And in this case, the image appears inverted.
00:37
It's a real image so that there's real light that gathers there.
00:42
And the object in image size are identical.
00:48
And so just kind of a reminder about the places to put objects and what they create for a concave mirror.
00:57
And then we'll do the analysis with the imaging.
01:02
Mirror equation and the magnification equation.
01:07
So if you put the object anywhere between c and f, you will create a magnified, real, and inverted.
01:26
If you put the object out further, okay, way out there, way out past the center of curvature, you will create a demagnified or smaller image, real and inverted.
01:50
And if you put the object between the focal point and the surface of the mirror, you will create a virtual, magnified and virtual.
02:04
So concave mirrors are very interesting, virtual and upright.
02:16
And one of the fun things to do is to take an object, suspended, and set it into pendulum motion near a concave mirror.
02:26
And you can see all these effects happen as the object swings back and forth.
02:33
But let's check out the center of curvature.
02:37
So we're going to write the mirror equation or the imaging equation as some places call it.
02:51
It says that the one over the focal length of the mirror is 1 over s plus 1 over s prime.
03:05
Whereas the magnification m is minus s prime over s with a negative sign, just saying whether the image is inverted or not.
03:16
But here we want s to be equal to s prime so that we get a magnification of minus 1.
03:25
And this means that the image is the same size as the object...