An object is placed 30 cm in front of a converging lens of focal length 10 cm. At what distance from the lens is the image formed?
Answer and explanation
Correct answer: A. 15 cm
- Step 1: Use 1/f = 1/do + 1/di. Step 2. 1/di = 1/10 - 1/30, so di = 15 cm. Answer: 15 cm. Why not the others: 7.5 cm: this adds the reciprocals instead of subtracting. 20 cm: this subtracts the distances directly. 40 cm: this adds the object distance and the focal length.
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