(A) Person $A$ hears two sounds: one from their own source (frequency $n$) and one reflected/received from person $B$'s source.Since $A$ is moving tow

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(A) Person $A$ hears two sounds: one from their own source (frequency $n$) and one reflected/received from person $B$'s source.Since $A$ is moving towards $B$ with speed $u$ and $B$ is stationary, the frequency $n'$ heard by $A$ from $B$'s source is given by the Doppler effect formula: $n' = n \left( \frac{v + u}{v} \right)$.The number of beats heard per second is the difference between the frequency heard from $B$ and the frequency of $A$'s own source.Beat frequency $= n' - n = n \left( \frac{v + u}{v} \right) - n$.Beat frequency $= n \left( \frac{v + u - v}{v} \right) = \frac{nu}{v}$.

Class 11 Physics Waves and Sound Doppler’s Effect

Medium

Two persons $A$ and $B$, each carrying a source of sound of frequency $n$, are standing a few metres apart in a quiet field. $A$ starts moving towards $B$ with a speed $u$. If $v$ is the speed of sound, the number of beats heard per second by $A$ will be

A
$\frac{nu}{v}$
B
$\frac{2nu}{v}$
C
$\frac{nu}{v+u}$
D
$\frac{nu}{v-u}$

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Class 11

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Chapter

Waves and Sound

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Doppler’s Effect

$A$ siren emitting a sound of frequency $800 \, Hz$ moves away from an observer towards a cliff at a speed of $15 \, m s^{-1}$. The frequency of sound that the observer hears in the echo reflected from the cliff is .... $Hz$ (Take velocity of sound in air $= 330 \, m s^{-1}$)

MediumNEET 2016

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$A$ person driving a car at a constant speed of $15\,m/s$ is approaching a vertical wall. The person notices a change of $40\,Hz$ in the frequency of his car's horn upon reflection from the wall. The frequency of the horn is ............ $Hz$. (Given: Speed of sound: $330\,m/s$)

DifficultJEE MAIN 2023

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Two stationary sources each emit waves of wavelength $\lambda$. An observer moves from one source to the other with velocity $u$. The number of beats heard by the observer is:

DifficultAIPMT 2000

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An observer moves towards a stationary source of sound with a speed $\frac{1}{5}^{\text{th}}$ of the speed of sound. The wavelength and frequency of the waves emitted by the source are $\lambda$ and $f$ respectively. The apparent frequency and wavelength heard by the observer are respectively,

MediumAIPMT 2003

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$A$ car moving towards a cliff emits sound of frequency '$n$'. If the difference in frequencies of the horn and its echo heard by the driver of the car is $10 \%$ of '$n$',then the speed of the car is nearly (Speed of sound in air is $336 \ m/s$) (in $m/s$)

MediumTS EAMCET 2025

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Two persons $A$ and $B$, each carrying a source of sound of frequency $n$, are standing a few metres apart in a quiet field. $A$ starts moving towards $B$ with a speed $u$. If $v$ is the speed of sound, the number of beats heard per second by $A$ will be

Similar Questions

$A$ siren emitting a sound of frequency $800 \, Hz$ moves away from an observer towards a cliff at a speed of $15 \, m s^{-1}$. The frequency of sound that the observer hears in the echo reflected from the cliff is .... $Hz$ (Take velocity of sound in air $= 330 \, m s^{-1}$)

$A$ person driving a car at a constant speed of $15\,m/s$ is approaching a vertical wall. The person notices a change of $40\,Hz$ in the frequency of his car's horn upon reflection from the wall. The frequency of the horn is ............ $Hz$. (Given: Speed of sound: $330\,m/s$)

Two stationary sources each emit waves of wavelength $\lambda$. An observer moves from one source to the other with velocity $u$. The number of beats heard by the observer is:

An observer moves towards a stationary source of sound with a speed $\frac{1}{5}^{\text{th}}$ of the speed of sound. The wavelength and frequency of the waves emitted by the source are $\lambda$ and $f$ respectively. The apparent frequency and wavelength heard by the observer are respectively,

$A$ car moving towards a cliff emits sound of frequency '$n$'. If the difference in frequencies of the horn and its echo heard by the driver of the car is $10 \%$ of '$n$',then the speed of the car is nearly (Speed of sound in air is $336 \ m/s$) (in $m/s$)

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