Problem 10.5. A parallel light beam is diverged by a concave lens of focal length -12.5cm and then made parallel once more by a convex lens of focal length 50cm. How far are the two lenses apart.
Data
Focal length of first lens.f1 = -12.5cm
Focal length of 2nd lens f2 =50cm
Find .?
Distance between two lens l.=?
Solution
When a beam parallel rays are diverged by concave lens And again made paralleld by a concave lens then principal focus of both lens must be at same point. In this case the distance between lens is given by
L= f1 +f2 = -12.5+50 =37.5cm
L=37.5cm
Answer
