Q121 / 180 · KCET 2012 · Physics

Intensity level of sound whose intensity is $10^{-8} \mathrm{Wm}^{-2}$ is

  • A
    $80 \mathrm{~dB}$
  • B
    $8 \mathrm{~dB}$
  • C
    $4 \mathrm{~dB}$
  • Correct answer
    D
    $40 \mathrm{~dB}$

Solution

Intensity level of sound $=10 \log \frac{\mathrm{I}}{\mathrm{I}_{0}} \mathrm{~dB}$ $$ \begin{aligned} =10 \log \left(\frac{10^{-8}}{10^{-12}}\right) \mathrm{dB} &=40 \mathrm{~dB} \\ &\left.\because \mathrm{I}_{0}=10^{-12} \mathrm{~W} / \mathrm{m}^{2}\right) \end{aligned} $$

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

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