G L Mittal and TARUN MITTAL Solutions for Chapter: Doppler Effect, Exercise 2: NUMERICALS

With what velocity should an observer go away from a stationary source of sound so that the frequency of the sound as heard by him is half of the actual frequency ?

With what velocity should a source of sound travel towards a stationary observer so that the apparent frequency may be double of the actual frequency? Velocity of sound is $340 \mathrm{m}/\mathrm{s}$.

Two trains are approaching each other with the speeds of $72 \mathrm{km}/\mathrm{h}$. The frequency of the whistle of one train as heard by a passenger on the other train is $700 \mathrm{Hz}$. Find : (i) the real frequency of the whistle before the trains meet and (ii) the frequency of the whistle heard by the passenger when the trains have crossed each other.

Two trains are approaching each other with the speeds of $72 \mathrm{km}/\mathrm{h}$. The frequency of the whistle of one train as heard by a passenger in the other train is $700 \mathrm{Hz}$. Find : (i) the real frequency of the whistle and (ii) the frequency of the whistle heard by the passenger when the trains have crossed each other.

Two trains, both at $108 \mathrm{km}/\mathrm{h}$ speed, cross each other. One of the trains whistles whose frequency is $750 \mathrm{Hz}$. What frequency will be heard by a passenger in the other train (i) before crossing, (ii) after crossing ?

Two trains, both at $108 \mathrm{km}/\mathrm{h}$ speed, cross each other. One of the trains whistles whose frequency is $750 \mathrm{Hz}$. What frequency will be heard by a passenger in the other train (i) before crossing,(ii)after crossing?

A whistling engine, whose frequency is $1240 \mathrm{Hz}$, is going towards a hill with a speed of $72 \mathrm{km}/\mathrm{h}$. The driver of the engine hears an echo of the whistle. Find the frequency of the echo as heard by him.

A table is revolving about its axis at a rate of $5$ revolutions per second. A sound-source (frequency $1000 \mathrm{Hz}$) is fixed in the table at a distance of $0.70 \mathrm{m}$ from the axis. Calculate the maximum and minimum frequencies as heard by a listener standing at a distance from the table. The speed of sound at the room temperature is $352 \mathrm{m}/\mathrm{s}$.