In a large room, a person receives direct sound waves from a source 120 m away from him. He also receives waves from the same source after being reflected from the 25 m high ceiling, at a point halfway between them. The two waves interfere constructively for a wavelength of

Question

In a large room, a person receives direct sound waves from a source 120 m away from him. He also receives waves from the same source after being reflected from the 25 m high ceiling, at a point halfway between them. The two waves interfere constructively for a wavelength of, 20 , 20 3 , 20 5 , e t c, 10 , 5 , 2.5 , e t c, 10 , 20 , 30, e t c, 15 , 25 , 35 , e t c

MARKS App · Accepted Answer

Path difference between the waves Δ x = 130 - 120 = 10 m As phase between the two waves is π because reflection takes place from the rigid end, so for constructive interference. Δ x = 2 n + 1 λ 2 10 = 2 n + 1 λ 2 ∴ λ = 20 2 n + 1 n = 0 , λ 1 = 20 m n = 1 , λ 2 = 20 3 m n = 2 , λ 3 = 20 5 m

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