JEE PYQ: Waves And Sound Question 37
Question 37 - 2019 (12 Apr Shift 2)
A small speaker delivers 2 W of audio output. At what distance from the speaker will one detect 120 dB intensity sound? [Given reference intensity of sound as $10^{-12}$ W/m$^2$]
(1) 40 cm
(2) 20 cm
(3) 10 cm
(4) 30 cm
Show Answer
Answer: (1)
Solution
Using, $\beta = 10\log_{10}\left(\frac{I}{I_0}\right)$
$120 = 10\log_{10}\left(\frac{I}{10^{-12}}\right)$ …(i)
Also $I = \frac{P}{4\pi r^2} = \frac{2}{4\pi r^2}$ …(ii)
On solving above equations, we get $r = 40$ cm.
BETA
