A source of sound operates at 20 kHz, 20 W emitting sound uniformly in all directions. The speed of sound in air is 340 m s-1 and the density of air is 1.2 kg m-3. (a) What is the intensity at a distance of 60 m from the source? (b) What will be the pressure amplitude at this point? (c) What will be the displacement amplitude at this point?
Given:
Velocity of sound in air 
Power of the source 
Frequency of the source 
Density of air 
(a)Distance of the source 
Intensity is given by:
Where, A is the area.
⇒
⇒
(b) As we know,
⇒ 
⇒
⇒
(c) As we know,
= the displacement amplitude.
⇒ 
On applying the respective values, we get:
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