Photography Optics: The focal length of the lens of a simple film camera is 40.0 mm. By what amount should the distance between the lens and the film be increased or decreased to change the focus from a person who is 25 m from the lens to one who is 4.0 m from the lens?
A. 0.2 mm
B. 0.3 mm
C. 0.4 mm
D. 0.5 mm
E. 0.7 mm
Answer: B
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