c Relative motion apart decreases frequency. The greater the relative speed, the greater the effect. The Doppler effect occurs not only for sound, but for any wave when there is relative motion between the observer and the source
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An observer is riding on a bicycle and moving towards a hill at $18\,km\,h ^{-1}$. He hears a sound from a source at some distance behind him directly as well as after its reflection from the hill. If the original frequency of the sound as emitted by source is $640\,\,Hz$ and velocity of the sound in air is $320\,m / s$, the beat frequency between the two sounds heard by observer will be $...Hz$.
The displacement y of a particle in a medium can be expressed as: $y = {10^{ - 6}}\sin (100t + 20x + \pi /4)m,$ where $t$ is in second and $x$ in meter. The speed of wave is ... $m/s$
Column $I$ shows four systems, each of the same length $L$, for producing standing waves. The lowest possible natural frequency of a system is called its fundamental frequency, whose wavelength is denoted as $\lambda_{ f }$. Match each system with statements given in Column $II$ describing the nature and wavelength of the standing waves.
The equation of displacement of two waves are given as ${y_1} = 10\sin \left( {3\pi t + \frac{\pi }{3}} \right)$; ${y_2} = 5(\sin 3\pi t + \sqrt 3 \cos 3\pi t)$. Then what is the ratio of their amplitudes
A uniform string oflength $20\ m$ is suspended from a rigid support. A short wave pulse is introduced at its lowest end. It starts moving up the string. The time taken to reach the supports is (take $g= 10 $ $ms^{-2}$ )
$Assertion :$ Doppler formula for sound wave is symmetric with respect to the speed of source and speed of observer.
$Reason :$ Motion of source with respect to stationary observer is not equivalent to the motion of an observer with respect to stationary source.
A progressive wave travelling in positive by $x-$ direction given by $y = a\, sin (kx -\omega t)$ meets fixed end at $x = 0$. The reflected wave may be given by