If the focal length of a camera lens is 20cm, the distance from the film...
PHYSICS
JAMB 1993
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: C. 25cm
Explanation
F = \(\frac{uv}{u + v}\)
20 = \(\frac{100 \times v}{100 + v}\)
v = 25cm
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