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Per NCERT, what is the sign convention for FOCAL LENGTH (f) of a CONVEX lens vs a CONCAVE lens?
ABoth negative
BConvex lens: f is POSITIVE; Concave lens: f is NEGATIVE
CBoth positive
DConvex negative, concave positive
Answer & Solution
Correct answer: B. Convex lens: f is POSITIVE; Concave lens: f is NEGATIVE
Per NCERT §9.3.6, convex f > 0; concave f < 0 (per the New Cartesian convention).
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