If the focal length of a camera lens is 20cm, the distance from the film at which the lens must be set to produce a sharp image of an object 100cm away is
-
A.
17cm -
B.
20cm -
C.
25cm -
D.
100cm
Correct Answer: Option C
Explanation
F = (frac{uv}{u + v})
20 = (frac{100 times v}{100 + v})
v = 25cm