Q

How many principal foci does a lens have?

RRB NTPC (Graduate Level) (Stage-II); RRB JE (Stage-I) 13/10/2025 / Shift-I; 18/12/2024 / Shift-III 2025; 2024
✓ Answer: B 2
A lens has two principal foci, one for light incident from each side.
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