00:01
We're going to talk about image formation in a concave mirror.
00:05
So consider that we have a concave mirror whose radius of curvature is equal to r.
00:13
This is the radius of curvature.
00:15
Then the focal length, f, of this mirror, is equal to the radius of curvature divided by two.
00:27
It's half the radius of curvature.
00:28
Let's say we have an object located at a distance o from the mirror, and we want to know at what distance i the image is formed, i, the image is formed, i'm sorry.
00:45
Let's say that the image is formed at this distance here.
00:52
Then we know that 1 over the focal length is equal to 1 over the distance between the mirror and the image.
01:02
Plus one over the distance between the mirror and the object.
01:09
Furthermore, if the distance between the mirror and the object o is greater than the focal length for a concave mirror, then the image will be real.
01:26
And finally, we need to remember that the magnification of an image is equal to minus the distance between the mirror and the image divided by the distance between the mirror and the object.
01:42
In our case, we have a mirror that has a radius of curvature 20 centimeters, a concave mirror, and in question a, we have to find the distance of the image between the image and the mirror in three different cases.
02:03
In the first case, when we have an object that is located at a distance of 10 centimeters, actually i'm sorry, of 40 centimeters from the mirror.
02:21
So we can isolate i in our equation.
02:24
So 1 over i is equal to 1 over f minus 1 over 0, meaning that i is 1 over 1 over f minus 1 over 0.
02:40
So this is 1 over 1 over f is 1 over f is 1 over 0.
02:42
So this is 1 over 1 over f is 1 over r over 2 notice that f is 10 centimeters so 1 over 10 minus 1 over 40 so this is 1 over 30 divided by 400 this is 400 divided by 30 or 13 .3 centimeters then question 2 always equal to 20 centimeters so i will be 1 over 1 over 20 minus 1 over 40.
03:24
This is 1 over 20 over 400 or 20 centimeters.
03:29
This is the distance between the image and the mirror.
03:34
In question 3, 0 is equal to 10 centimeters...