Calculate Intensity of Sound Wave at Cliff from Radio Source

AI Thread Summary
Michelle's picnic across the valley from a cliff involves calculating sound wave intensity from her radio. The echo from the cliff takes 1.2 seconds to return, indicating the cliff is 206 meters away, based on the speed of sound at 343 m/s. For the intensity calculation, the intensity at 1 meter from the radio is 1.0 x 10^-5 W/m², and intensity decreases with distance squared. A user struggles to find the intensity at the cliff, initially calculating it as 2.35 x 10^-5 W/m² but receives feedback indicating this is incorrect. The discussion centers on clarifying the calculations for sound intensity based on distance.
kokenwa
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Homework Statement


Michelle is enjoying a picnic across the valley from a cliff. She is playing music on her radio (assume it to be an isotropic source) and notices an echo from the cliff. She claps her hands and the echo takes 1.2 s to return.
(a) Given that the speed of sound in air is 343 m/s on that day, how far away is the cliff?
-i got the correct answer for this one, and it was 206m


(b) If the intensity of the music 1.0 m from the radio is 1.0 10-5 W/m2, what is the intensity of the music arriving at the cliff?


i can't find the answer for b. can someone help me out?
 
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Intensity is proportional to 1/r^2.

That is, if the source is twice as far away, the intensity is 1/4; three times as far away, 1/9 etc...
So if the source is 206 times as far away...?
 
i put in 2.35 x 10^-5 and it was still wrong
 
how did you get 2.35 x 10^-5 ? - show your working.

this is not what I got.
 

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