00:01
So we have two lenses.
00:03
We have lens l1 and then we have an l lens l2.
00:07
The first lens l1 is a diverging lens and its focal length is negative 10 centimeters.
00:14
The second lens is a converging lens and the focal length is 30 centimeters.
00:19
And the two lenses are 20 centimeters apart.
00:28
And an object is placed 10 centimeters from l1.
00:34
So do is 10 centimeters.
00:40
So we have to find the final image.
00:43
Now, for finding the final image, we can first find the image formed by l1, and then the image becomes the object for l2.
00:50
So we start with 1 over do plus 1 over d .i is equal to 1 over f, and this would be 1 over 10, plus 1 over d .i is equal to negative 1 over 10, or 1 over d .i, is equal to negative 1 over 10 minus 1 over 10.
01:11
So, the i is equal to negative 5 centimeters.
01:17
So this means that this image is formed to the left of l1.
01:23
So the image is formed somewhere around here.
01:27
So this is the image.
01:29
Now we're going to take this image and make it the object for l2...