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Velocity of sound waves in air is 330 m/s. For a particular sound wave in air, a path difference of 40 cm is equivalent to phase difference of 1.6π. The frequency of this wave is

Asked in NEET 1990 · Interference of two waves

Answer: (3) 660 Hz

Step-by-step solution

Given: v=330 m/s, Δ x=40 cm =0.4 m, Δφ=1.6π.

Idea: path and phase are proportional, with a whole wavelength worth 2π.

Δφ=(2π)/λΔ x, so λ=(2π Δ x)/(Δφ).

λ=(2π×0.4)/(1.6π)=(0.8)/(1.6).

λ=0.5 m.

f=v/λ=(330)/(0.5)=660 Hz.

Why the other options are wrong

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