Wave Mechanics Question 621

Question: A transverse wave is represented by $ y=A\sin (\omega t+kx) $ . For what value of the wavelength is the wave velocity equal to the maximum particle velocity?

Options:

A) $ \frac{\pi A}{2} $

B) $ \pi A $

C) $ 2\pi A $

D) $ A $

Show Answer

Answer:

Correct Answer: C

Solution:

[c] $ y=A\sin (\omega t-kx) $ Particle velocity, $ v _{p}=\frac{dy}{dt}=A,\omega \cos (\omega t-kx) $
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Therefore {v _{p,\max }}=A,\omega $ wave velocity $ =\frac{\omega }{k} $
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Therefore ,A,\omega =\frac{\omega }{k} $

$ i.e.,A=\frac{1}{k} $ But $ k=\frac{2\pi }{\lambda } $
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Therefore \lambda =2\pi A $