  Question

Of the following, the equation of plane progressive wave is:

A
y=rsinωt  B
y=rsin(ωtkx)  C
y=arsin(ωtkx)  D
y=arsin(ωtkt)  Solution

The correct option is B $$y=r\sin(\omega t-kx)$$For simple harmonic motion, the displacement at any instant of time is given by$$y=A \sin \omega t$$ .......(1)Where A is the amplitude and $$\omega$$ is the angular frequency of the wave. Consider a particle P at a distance x from the particle O on its right. Let the wave travel with a velocity v from left to right. Since it takes some time for the disturbance to reach P, its displacement can be written as $$y=A \sin (\omega t-\phi)$$ .......(2)Where $$\phi$$ is the phase difference between the particles O and P.We know that a path difference of $$\lambda$$ corresponds to a phase difference of $$2\pi$$ radians. Hence a path difference of x corresponds to a phase difference of $$\phi = \frac{2\pi}{\lambda}x$$. Now the propagation vector k is defined as $$k = \frac{2\pi}{\lambda}$$....(3)Substituting equation (3) in equation (2)We get, $$y=A\sin(\omega t-kx)$$Physics

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