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
Verified Correct Answer: C.
Physical Principles & Numerical Solution
F = \(\frac{uv}{u + v}\)
20 = \(\frac{100 \times v}{100 + v}\)
v = 25cm
Source: Myschool Past Questions Archive (Record #28005)