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14.Waves and Sound
normal
Four sources of sound each of sound level $10\,dB$ are sounded together, there sultant intensity level will be ... $dB$
A
$40$
B
$26$
C
$16$
D
$13$
Solution
Loudness (in $\mathrm{dB})=10 \log _{10}\left(\frac{\mathrm{I}}{\mathrm{I}_{\mathrm{o}}}\right)=10$
$\Rightarrow \mathrm{I}=10 \mathrm{I}_{\mathrm{o}}$
When all four sources are sounded together total intensity $\mathrm{I}_{\max }=4 \mathrm{I}=40 \mathrm{I}_{\mathrm{o}}$
$\therefore$ Loudness in $(\mathrm{dB})=10 \log _{10}\left(\frac{40 \mathrm{I}_{\circ}}{\mathrm{I}_{\circ}}\right)$
$=10 \log _{10}(40) \approx 16 \mathrm{\,dB}$
Standard 11
Physics
