For sound waves travelling in dry air at normal pressure the speed varies with…

PHYSICS · Multi-part · CBSE · Physics · Waves · Waves

Problem

For sound waves travelling in dry air at normal pressure the speed vv varies with Celsius temperature θ\theta according to the empirical relation v=331+0.6 θ  m s−1v = 331 + 0.6\,\theta\;\text{m}\,\text{s}^{-1}. A tuning fork of frequency 1024 Hz1024\,\text{Hz} is sounded successively in air at 0∘C0^{\circ}\text{C} and then in air at 30∘C30^{\circ}\text{C}. (i) Derive an expression for the wavelength λ\lambda of the sound in air as a function of the temperature θ\theta, keeping the frequency constant. (ii) Using the expression obtained in (i), calculate the wavelength at 0∘C0^{\circ}\text{C} and at 30∘C30^{\circ}\text{C}. (iii) Find the fractional change in wavelength per degree Celsius between these two temperatures. (iv) Comment on the practical significance of this temperature dependence for precise acoustic measurements.

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