00:01
So we have two lenses, l1 and l2, and the two lenses are a distance 24 centimeters apart.
00:14
And for both of them the focal length is given as 12 centimeters and because these are converging denses so the focal length is positive.
00:23
And now we have an object which is placed at distance d .o.
00:29
Equal to 36 centimeters from the lens on the left.
00:35
And we want to find the distance of the final image from the lens l2.
00:42
Now, since it's a combination of lenses, we will first find the distance of image formed by l1, and that becomes the object for l2.
00:50
So we start with the thin lens formula, 1 over do, plus 1 over d .i is equal to 1 over f.
00:57
So 1 over 36 plus 1 over d .i.
01:02
Is equal to 1 over 12...