Q103 / 120 · JEE Main 2007 · Physics

A sound absorber attenuates the sound level by $20 \mathrm{~dB}$. The intensity decreases by a factor of

  • A
    $1000$
  • B
    $10000$
  • C
    $10$
  • Correct answer
    D
    $100$

Solution

$\begin{aligned} & \mathrm{B}_1=10 \log \left(\frac{\mathrm{I}}{\mathrm{I}_0}\right) \\ & \mathrm{B}_2=\log \left(\frac{\mathrm{I}^{\prime}}{\mathrm{I}_0}\right) \end{aligned}$ given $B_2-B_1=20$ $\begin{aligned} & 20=10 \log \left(\frac{\mathrm{I^{\prime}}}{\mathrm{I}}\right) \\ & \mathrm{I}^{\prime}=100 \mathrm{I} \end{aligned}$

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

More Waves and Sound Questions