A car moves towards a hill with speed $v_c$. It blows a horn of frequency $f$ which is heared by an observer following the car with speed $v_0$. The speed of sound in air is $v$.
Advanced
Download our app for free and get started
Speed of the car $=v_{c},$ frequency $=f$
Speed of the observer $=v_{o}$
Let, the speed of sound $=v$
$V=\lambda f[\lambda=\text { wavelength }]$
$\Rightarrow\left(v-v_{c}\right)=\lambda f$
$\Rightarrow \lambda=\frac{v-v_{c}}{f}$
The beat frequency observed by the observer $f_{b}=\frac{\left(v+v_{o}\right)}{\left(v-v_{c}\right)} \times \frac{2 f v_{c}}{\left(v+v_{c}\right)}=\frac{2 v_{c}\left(v+v_{c}\right) f}{v^{2}-v_{c}^{2}}$
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1The vibration of a string fixed at both ends are described by $Y= 2 \,\,sin(\pi x) \,\,sin\,\,(100\pi t)$ where $Y$ is in $mm$,$x$ is in $cm$,$t$ in $sec$ thenView Solution
- 2A $1 cm$ long string vibrates with fundamental frequency of $256\, Hz$. If the length is reduced to $\frac{1}{4}cm$ keeping the tension unaltered, the new fundamental frequency will beView Solution
- 3Two open organ pipes of length $60 \mathrm{~cm}$ and $90 \mathrm{~cm}$ resonate at $6^{\text {th }}$ and $5^{\text {th }}$ harmonics respectively. The difference of frequencies for the given modes is . . . . . $\mathrm{Hz}$.View Solution
(Velocity of sound in air $=333 \mathrm{~m} / \mathrm{s}$ )
- 4A policemen buzz a whistle of frequency $400\ Hz$. A car driver is approaching the policemen. The speed of car is $54\ kmh^{-1}$. The change in frequency experienced by the driver, when driver approaches the policemen and after he crosses the policemen, is ... $Hz$ [Velocity of sound is $350\ ms^{-1}$]View Solution
- 5The frequency of the sinusoidal wave $y = 0.40\cos [2000\,t + 0.80\,x]$ would beView Solution
- 6Two sitar strings, $A$ and $B,$ playing the note $'Dha'$ are slightly out of tune and produce beats and frequency $5\,Hz.$ The tension of the string $B$ is slightly increased and the beat frequency is found to decrease by $3\,Hz$ . If the frequency of $A$ is $425\,Hz,$ the original frequency of $B$ is ... $Hz$View Solution
- 7An iron block is dropped into a deep well. Sound of splash is heard after $4.23 \,s$. If the depth of the well is $78.4 \,m$, then find the speed of sound in air is ............ $m / s$ $\left(g=9.8 \,m / s ^2\right)$View Solution
- 8A closed pipe of length $300 \,cm$ contains some sand. A speaker is connected at one of its ends. The frequency of the speaker at which the sand will arrange itself in $20$ equidistant piles is close to .......... $kHz$ (velocity of sound is $300 \,m / s )$View Solution
- 9Intensity level $200 cm$ from a source of sound is $80 dB$. If there is no loss of acoustic power in air and intensity of threshold hearing is ${10^{ - 12}}W{m^{ - 2}}$ then, what is the intensity level at a distance of $400 cm$ from source .... $dB$View Solution
- 10A source of sound emits $200\pi W$ power which is uniformly distributed over a sphere of $10 m$ radius. What is the loudness of sound on the surface of a sphereView Solution