A converging lens has focal length 20 cm. An object is placed 30 cm from it. At what distance is the image formed?
Answer and explanation
Correct answer: D. 60 cm
- Step 1: Use the lens equation 1/f = 1/u + 1/v, so 1/v = 1/f - 1/u.
- Step 2: 1/v = 1/20 - 1/30, giving v = 60 cm.
Answer
60 cm.
Why not the others: '50 cm' adds the object distance and the focal length; '10 cm' subtracts the focal length from the object distance; '600 cm' multiplies instead of using the reciprocal formula.
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