alleryPower of a lens of focal length 20 cm (in dioptres):
A20
B5 (= 1/0.20)
C0.5
D-5
Answer & Solution
Correct answer: B. 5 (= 1/0.20)
P = 1/f (f in meters).
f = 0.20 m, so P = 5 D. Convex lens: positive. Concave: negative.
**Combined lenses in contact:** P = P₁ + P₂.
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