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
A) $8 \times 10^{- 6}W/m^{2}$
B) $2 \times 10^{- 4}W/m^{2}$
C) $1 \times 10^{- 4}W/m^{2}$
D) $4\ W/m^{2}$
Explanation
(a) Intensity $= \frac{Power}{Area} = \frac{4}{4\pi \times (200)^{2}} = 7.9 \times 10^{- 6}W/m^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.