Gujarati
14.Waves and Sound
medium

The rope shown at an instant is carrying a wave travelling towards right, created by a source vibrating at a frequency $n$. Consider the following statements

$I.$ The speed of the wave is $4n \times ab$

$II.$ The medium at $a$ will be in the same phase as $d$ after $\frac{4}{{3n}}s$

$III.$ The phase difference between $b$ and $e$ is $\frac{{3\pi }}{2}$

Which of these statements are correct

A

$I, II$ and $ III$

B

$II$ only

C

$I$ and $III$

D

$III$ only

Solution

(c) Speed = $n\lambda $= $n(4ab) = 4n \times ab$               $\left( {{\rm{As}}\,ab = \frac{\lambda }{4}} \right)$

Path difference between $b$ and $e$ is $\frac{{3\lambda }}{4}$

So the phase difference =$\frac{{2\pi }}{\lambda } \times $Path difference 

= $\frac{{2\pi }}{\lambda }.\frac{{3\lambda }}{4} = \frac{{3\pi }}{2}$

Standard 11
Physics

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