Q47 / 150 · MHT CET 2021 (21 Sep Shift 1) · Chemistry

The wavelength of a spectral line of caesium is $460 \mathrm{~nm}$. What is the frequency of spectral line?

  • A
    $4.5 \times 10^8 \mathrm{~Hz}$
  • Correct answer
    B
    $6.5 \times 10^{14} \mathrm{~Hz}$
  • C
    $3 \times 10^9 \mathrm{~Hz}$
  • D
    $5.6 \times 10^{14}$

Solution

$$ \begin{aligned} & v=\frac{\mathrm{c}}{\lambda}\left(1 \mathrm{~nm}=10^{-9} \mathrm{~m}\right) \\ & =\frac{3 \times 10^8}{460 \times 10^{-9}} \\ & =6.5 \times 10^{14} \mathrm{~Hz} \end{aligned} $$

Hence, the correct answer is option: 'B'.

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