00:01
So we have a lens, which is a diverging lens, and there's a mirror which is a concave mirror or it's a converging mirror.
00:14
And then the focal length of the lens is negative 8 .0 centimeters, whereas the focal length of the mirror is 12 .0 centimeters.
00:24
And the two are a distance of 30 centimeters apart.
00:32
And an object is placed 20 centimeters from the lens.
00:39
And what we need to do here is we need to find the image location, the location of the final image in part a.
00:48
So since it's a combination, we'll first find where the image is formed by l1 and then we will use that as the object for m.
00:56
So we start with 1 over do plus 1 over d .i is equal to 1 over f.
01:02
Do for the lens is 20 centimeters.
01:06
We're trying to figure out di, and the focal length for the lens is negative 8.
01:12
So 1 over di is equal to negative 1 over 8 minus 1 over 20, and that gives di is equal to negative 5 .71 centimeters.
01:26
So the image is formed 5 .71 centimeters to the left of the lens.
01:35
So that means that the overall distance from the mirror would be 30 plus 5 .71.
01:44
So now we can start talking about the mirror...