K K Sharma Solutions for Chapter: Waves, Exercise 1: TOPICWISE QUESTIONS

Two sound sources $S_1$ and $S_2$ have frequencies $224 \mathrm{Hz}$ and $220 \mathrm{Hz}$ respectively, and are situated at some distance. An observer is moving on the line joining the sources. If the observer does not hear beats, his speed will be: (Given the velocity of sound, $v=344 \mathrm{m} {\mathrm{s}}^{-1}$.)

A boy is walking away from a stationary wall at a speed of $1 \mathrm{m}/\mathrm{s}$ and blows a whistle whose frequency is $680 \mathrm{Hz}$. The number of beats heard by the boy per second is (Velocity of sound in air$=340 \mathrm{m}/\mathrm{s}$)

As shown in the figure, a source $O$ of frequency $300 \mathrm{Hz}$ moves towards north with a velocity of $30 \mathrm{m} {\mathrm{s}}^{-1}.$ $A, B, C$ and $D$ are four observers, each at a distance of $300 \mathrm{m}$ from $O$. Velocity of sound is $330 \mathrm{m} {\mathrm{s}}^{-1}.$ As the source starts moving in the direction shown at $t = 0$, the frequency observed by $A, B, C$ and $D$ will be,

As shown in the figure, a source $O$ of frequency $300 \mathrm{Hz}$ moves towards north with a velocity of $30 \mathrm{m} {\mathrm{s}}^{-1}$. $A, B, C$ and $D$ are four observers, each at a distance of $300 \mathrm{m}$ from $O$. Velocity of sound is $330 \mathrm{m} {\mathrm{s}}^{-1}.$ As the source starts moving in the direction shown at $t = 0$, the frequency observed by $A, B, C$ and $D$ at $t=5 \mathrm{s}$ will be:

A source emits waves of wavelength $60 \mathrm{cm}$. This source moves with a speed of $\frac{1}{5}\mathrm{th}$ of the speed of sound. The observer is on the north side. The apparent wavelengths of the waves in the north and south directions of the moving source will be:

A source of frequency $500 \mathrm{Hz}$ tied to the end of a string of length $1.2 \mathrm{m}$ revolves at $400 \mathrm{revolution} {\min }^{-1}$. A listener standing at large distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound $=340 \mathrm{m} {\mathrm{s}}^{-1}$)

A siren emitting sound of frequency $800 \mathrm{Hz}$ is going away from a static listener with a speed of $30 \mathrm{m}/\mathrm{s}.$ Frequency of sound that will be heard by the listener is (Velocity of sound $=330 \mathrm{m}/\mathrm{s}$),

A bus is moving with a velocity of $5 \mathrm{m} {\mathrm{s}}^{-1}$ towards a huge wall. The driver sounds a horn of frequency $165 \mathrm{Hz}$. If the speed of sound in air is $335 \mathrm{m} {\mathrm{s}}^{-1}$, then the number of beats heard by a passenger on the bus will be (Speed of sound $=335 \mathrm{m} {\mathrm{s}}^{-1}$)