Problem 10.15. Two converging lenses are 25 cm part. Focal length of each is 10 cm. An object is placed in front of one lens at 50 cm. Find the distance between the object and the final image?
Data
Focal length of each lens f1= f2 =f =10cm
Distance between lense l =25cm
Object distance from 1st lens p¹ =50 cm
To find
Distance between object and final image
Solution
For 1st lens 1/q1 =1/f1 - 1/p1 =1/10 - 1/50 = 5 -1/50
=4/50 = 50/4 = 12.5cm
P2 can be calculated as p2 = l1 - q1 = 25 - 12.5 = 12.5cm
For second lens = 1/q2 =1/f2 - 1/p2 = 1/10 - 1/12.5
= 12.5-10 /125 = 50cm
Putting these values in I we get d = 50+12.5 +12.5+56 =
D= 125cm
