A plane sound wave has average intensity 2 W/m² and crosses a surface of area 5 m² perpendicular to the direction of propagation. If the average power crossing the surface is N W, find N.
Physics · Wave Motion · sound wave
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Question

A plane sound wave has average intensity 2 W/m² and crosses a surface of area 5 m² perpendicular to the direction of propagation. If the average power crossing the surface is N W, find N.

G1 Physics · Accepted Answer

For normal incidence on the surface, P̄ = IA. Therefore, P̄ = 2×5 = 10 W. Hence, N = 10.