Doppler Effect

Consider a mixture of 2 mol of helium and 4 mol of oxygen. Compute the speed of sound in this gas mixture at 300 K.

A train standing at the outer signal of a railway station blows a whistle of frequency 400 Hz still air. The train begins to move with a speed of 10 ms^–1 towards the platform. What is the frequency of the sound for an observer standing on the platform? (sound velocity in air = 330 ms^–1)

Solve the following problem.

A police car travels towards a stationary observer at a speed of 15 m/s. The siren on the car emits a sound of frequency 250 Hz. Calculate the recorded frequency. The speed of sound is 340 m/s.

In discussing Doppler effect, we use the word "apparent frequency". Does it mean that the frequency of the sound is still that of the source and it is some physiological phenomenon in the listener's ear that gives rise to Doppler effect? Think for the observer approaching the source and for the source approaching the observer.

A sound source and listener are both stationary and a strong wind is blowing. Is there a Doppler effect?

The engine of a train sounds a whistle at frequency v. The frequency heard by a passenger is

A whistle producing sound waves of frequencies 9500 Hz and above is approaching a stationary person with speed v ms^-1. The velocity of sound in air is 300 ms^-1. If the person can hear frequencies up to a maximum of 10,000 HZ, the maximum value of v up to which he can hear the whistle is ______.

A sitar wire is replaced by another wire of same length and material but of three times the earlier radius. If the tension in the wire remains the same, by what factor will the frequency change?