1. Tardigrade
  2. Question
  3. Physics
  4. A straight line source of sound of length L=10 m, emits a pulse of sound that travels radially outward from the source. What sound energy (in mW ) is intercepted by an acoustic cylindrical detector of surface area 2.4 cm 2, located at a perpendicular distance 7 m from the source? The waves reach perpendicularly at the surface of the detector. The total power emitted by the source in the form of sound is 2.2 × 104 W. (Use π=22 / 7 )

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Q. A straight line source of sound of length $L=10\, m$, emits a pulse of sound that travels radially outward from the source. What sound energy (in $mW$ ) is intercepted by an acoustic cylindrical detector of surface area $2.4\, cm ^{2}$, located at a perpendicular distance $7\, m$ from the source? The waves reach perpendicularly at the surface of the detector. The total power emitted by the source in the form of sound is $2.2 \times 10^{4} W$. (Use $\pi=22 / 7$ )

Waves

Solution:

Imagine a cylinder of radius $7\, m$ and length $10\, m$.
Intensity of sound at the surface of cylinder is same everywhere.
Therefore $I=\frac{P}{2 \pi r L}$
(As sound is propagating radially out only, sound energy does not flow out through the ends)
$\therefore I=50\, W / m ^{2}$
Energy intercepted by the detector
$=I \times A=12\, mW$
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