Physicshard · Past Paper
A lens has a focal length of +10 cm. If an object is placed at 20 cm, the magnification is:
A-1
B+1
C-2
D+2
✓ Correct Answer: A — -1
u = -20, f = +10. 1/v = 1/10 - 1/20 = 1/20. v = 20. m = -v/u = -20/-20 = -1 (image is real/inverted).
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