A plane sound wave in air is represented by the excess-pressure equation Δp = 20 sin(4x-1360t), where Δp is in pascals and x and t are in SI units. Which option correctly gives the pressure amplitude, wave speed and direction of propagation?
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Question

A plane sound wave in air is represented by the excess-pressure equation Δp = 20 sin(4x-1360t), where Δp is in pascals and x and t are in SI units. Which option correctly gives the pressure amplitude, wave speed and direction of propagation?

Options

G1 Physics · Accepted Answer

Compare Δp = 20 sin(4x−1360t) with the standard progressive-wave form Δp = Δpₘ sin(kx−ωt). Hence, Δpₘ = 20 Pa, k = 4 rad/m, ω = 1360 rad/s. Wave speed is v = ω/k = 1360/4 = 340 m/s. Because the phase is kx−ωt, the wave travels in the +x direction. Correct option: A.

A plane sound wave in air is represented by the excess-pressure equation Δp = 20 sin(4x−1360t), where Δp is in pascals and x and t are in SI units. Which option correctly gives the pressure amplitude, wave speed and direction of propagation?