Two identical coherent sound sources individually produce intensity I₀ at a point. They are adjusted so that their pressure waves arrive exactly in phase at that point. By approximately how much does the sound-intensity level increase compared with the level due to one source alone?
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Question

Two identical coherent sound sources individually produce intensity I₀ at a point. They are adjusted so that their pressure waves arrive exactly in phase at that point. By approximately how much does the sound-intensity level increase compared with the level due to one source alone?

Options

G1 Physics · Accepted Answer

For two equal coherent waves arriving in phase, pressure amplitudes add. Therefore the resultant pressure amplitude becomes twice that due to one source. Since intensity is proportional to pressure-amplitude squared, I₂ = 4I₀. The rise in intensity level is Δβ = 10log₁₀[I₂/I₀] = 10log₁₀4 ≈ 6.02 dB. Correct option: B.