A spherical source of power 4 W and frequency 800 Hz is emitting sound waves. The intensity of waves at a distance 200 m is

Question

A spherical source of power 4 W and frequency 800 Hz is emitting sound waves. The intensity of waves at a distance 200 m is (A) 8 × 10-6 W / m 2 (B) 2 × 10-4 W / m 2 (C) 1 × 10-4 W / m 2 (D) 4 W / m 2

Tardigrade Admin · Accepted Answer

I=(I/A)=(I/4 π r2)=(4/4 π(200)2) =(1/4 × 104 × π)=0.079 × 10-4 =8 × 10-6 w / m 2

Q. A spherical source of power $4 W$ and frequency $800 Hz$ is emitting sound waves. The intensity of waves at a distance $200 m$ is

$8 \times 1 0^{- 6} W / m^{2}$

$2 \times 1 0^{- 4} W / m^{2}$

$1 \times 1 0^{- 4} W / m^{2}$

$4 W / m^{2}$

$I = \frac{I}{A} = \frac{I}{4 π r ^{2}} = \frac{4}{4 π ( 200 ) ^{2}}$
$= \frac{1}{4 \times 1 0 ^{4} \times π} = 0.079 \times 1 0^{- 4}$
$= 8 \times 1 0^{- 6} w / m^{2}$

Q. A spherical source of power 4W and frequency 800Hz is emitting sound waves. The intensity of waves at a distance 200m is

8×10−6W/m2

2×10−4W/m2

1×10−4W/m2

4W/m2