Physicsmedium · Past Paper
What is the power of a combination of a convex lens (f=20cm) and a concave lens (f=25cm)?
A+1 D
B-1 D
C+9 D
D-9 D
✓ Correct Answer: A — +1 D
P1 = 1/0.2 = 5D, P2 = 1/-0.25 = -4D. Total P = 5 - 4 = 1D.
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