00:01
In this problem, we have been given that there is an object which is placed at a distance of 25 cm from this diverging lens.
00:09
And the distance between the converging and diverging lens is 30 centimeter, provided that the final image is formed at a distance of 17 centimeter to the right of this converging lens.
00:22
And we have to determine the focal length of this diverging lens.
00:28
So let's consider this focus or the focal length of this diverging lens to be f.
00:36
And we have been given the focal length of this converging lens as 12 centimeter.
00:42
So first we observe that with respect to the diverging lens, let's consider with respect to the diverging lens.
00:54
Object distance is 25 centimeter.
00:58
And let's take that with you.
01:02
So that's minus 25 centimeter.
01:05
Also here, now we need to consider with respect to converging lens.
01:10
So together we will explore the situation.
01:13
So with respect to the converging lens, here the focal length is 12 centimeter because it's positive as it's converging lens.
01:21
The image distance as it's formed to the right, so it will be plus 17 centimeter.
01:26
And here when we use the lens formula, 1 by v minus 1 by u is equal to 1 by f.
01:32
We get the value of you as minus 40 .8 centimeter.
01:37
But here the separation itself is 30 centimeter.
01:40
That means the image is formed to the left of this diverging lens.
01:45
So definitely in this case, with respect to the diverging lens, we here will be minus 10 .8 because as it is formed 40 .8 centimeters.
01:58
So we will subtract from this 30 centimeter, which is the separation.
02:02
So that will be 10 .8 centimeter.
02:06
And here once again, we apply the lens formula.
02:09
1 by f is equal to 1 by v minus 1 by u.
02:13
And let's put the value.
02:15
We get 1 by f is equal to 1 by minus 10 .8 plus 1 by 25...