A converging lens has focal length 12 cm. An object is placed 20 cm from it. At what distance is the image formed?
Answer and explanation
Correct answer: C. 30 cm
- Step 1: Use the lens equation 1/f = 1/u + 1/v, so 1/v = 1/f - 1/u.
- Step 2: 1/v = 1/12 - 1/20, giving v = 30 cm.
Answer
30 cm.
Why not the others: '32 cm' adds the object distance and the focal length; '8 cm' subtracts the focal length from the object distance; '240 cm' multiplies instead of using the reciprocal formula.
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