8.6 cm
Explanation:
Step 1:
In this we have to find the focal length of converging lens.
To find focal length we have,
[tex](1/u) + (1/v) = (1/f)[/tex]
where u = Object distance
v= Image distance
f = Focal length
Step 2:
[tex](1/f) = (1/20) + (1/15)[/tex]
(1/f) = 0.116
f = 1/0.116
f = 8.6 cm
