Q81 / 90 · KVPY 2015 (SB/SX) · Physics

The intensity of sound during the festival season increased by 100 times. This could imply a decibel level rise from

A
20 to $120 \mathrm{~dB}$
B
$70$ to $72 \mathrm{~dB}$
C
100 to $10000 \mathrm{~dB}$
Correct answer
D
80 to $100 \mathrm{~dB}$

Solution

Sound intensity $=10 \log _{10}\left(\frac{I}{I_{0}}\right)$ $\mathrm{I}=100 \mathrm{I}_{0}$ so $10 \times \log \frac{100 i_{0}}{i_{0}}$ $=20$ So level rises by $20 \mathrm{~dB}$

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

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