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Per NCERT, what is the POWER (P) of a LENS — and what is its SI unit?
AP = f × something; unit is watt
BP = u × v; unit is dioptre
CP = focal length; unit is metre
DP = 1/f (reciprocal of focal length); SI unit is DIOPTRE (D), where 1 D = 1 m⁻¹
Answer & Solution
Correct answer: D. P = 1/f (reciprocal of focal length); SI unit is DIOPTRE (D), where 1 D = 1 m⁻¹
Per NCERT §9.3.8, lens power P = 1/f. Unit dioptre = 1 m⁻¹ (when f is in metres).
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