Per NCERT §1.2 (revised SI 2018), the second is defined via the caesium-133 hyperfine transition frequency Δν_Cs, fixed at which value?
A299 792 458 Hz
B9 192 631 770 Hz
C1.602 × 10⁻¹⁹ Hz
D6.626 × 10⁻³⁴ Hz
Answer & Solution
Correct answer: B. 9 192 631 770 Hz
NCERT Table 1.1: second is defined so Δν_Cs = 9 192 631 770 Hz exactly. Atomic frequency standard.
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