A plane sinusoidal sound wave has particle-displacement amplitude sₘ, angular frequency ω, equilibrium density ρ₀ and wave speed v. Which expression gives its average intensity I?
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A plane sinusoidal sound wave has particle-displacement amplitude sₘ, angular frequency ω, equilibrium density ρ₀ and wave speed v. Which expression gives its average intensity I?

G1 Physics · Accepted Answer

The average total energy density of a plane sinusoidal sound wave is ū = ½ρ₀ω²sₘ². The energy is transported with speed v. Therefore, I = ūv = ½ρ₀vω²sₘ². Using Δpₘ = ρ₀vωsₘ, the same result may also be written as I = Δpₘ²/(2ρ₀v). Correct option: B.