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JEE Main 2007

Exam: JEE Main
Year: 2007
Subject: Physics
Chapter: Waves and Sound

JEE Main 2007 · Physics · Waves and Sound

A sound absorber attenuates the sound level by 20 ~dB . The...

A sound absorber attenuates the sound level by

20 \mathrm{~dB}

. The intensity decreases by a factor of

Options

A $1000$
B $10000$
C $10$
D $100$

Correct answer

D. $100$

Step-by-step 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}

$$

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