In the acoustic interferometer in the figure, the speaker emits a sound of frequency 10 kHz and the distance L has been set such that the microphone picks up a maximum intensity. The upper arm (shaded section) is then immersed in liquid nitrogen, so that the temperature of the air in this region of the tube slowly drops from the ambient temperature of 27 ⁰C to -100 ⁰C. Given that the speed of sound in air at a temperature T (in Kelvin) is vsom = √(gamma*R*T/Mmolar) and treating air as a diatomic ideal gas (gamma = 7/5) of molar mass Mmolar = 28.88 g, calculate how many times the microphone will pick up minima of intensity during the process.
Assume R = 8.314 J/K.mol and consider that the air temperature does not change in the other sections of the interferometer.
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