How far from a +50-mm focal length lens, such as is used in many 35-mm cameras, must an object be placed so it will form a real image that is 3.0 times the size of the object?
A) 58 mm
B) 67 mm
C) 46 mm
D) 52 mm

Question

Quizplus · Accepted Answer

To form a real image that is 3 times the size of the object, the object distance (u) and image distance (v) must satisfy the lens formula 1/f = 1/u + 1/v and the magnification formula m = -v/u = 3. Solving these equations with f = 50 mm gives u ≈ 67 mm.

How Far from a +50-Mm Focal Length Lens, Such as Is