A small speaker delivers 2w of audio output. At a distance x cm from the speaker will one detect 120dB intensity of sound? [Given reference intensity of sound as $10^{- 12} w / m^{2}$ ]. Find value of x.

see full answer

Start JEE / NEET / Foundation preparation at rupees 99/day !!

21% of IItians & 23% of AIIMS delhi doctors are from Sri Chaitanya institute !!

An Intiative by Sri Chaitanya

answer is 40.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

Loudness of sound is given by $d B = 10 \log \frac{I}{I_{0}}$ [I is intensity of sound, $I_{0}$ is reference intensity of sound]
$∴ 120 = 10 \log (\frac{I}{I_{0}}) \Rightarrow I = 1 w / m^{2}$

Also $I = \frac{P}{4 π r^{2}} = \frac{2}{4 π r^{2}}$

$∴ r = \sqrt{\frac{2}{4 π}} = \sqrt{\frac{1}{2 π} m} = 0.399 m \approx 40 c m$

Watch 3-min video & get full concept clarity

hear from our champions

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Books for IIT JEE

Best Books for NEET

🔥 Start Your JEE/NEET Prep at Just ₹1999 / month - Limited Offer! Check Now!

Get Expert Academic Guidance – Connect with a Counselor Today!