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14.Waves and Sound
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A string fixed at one end is vibrating in its second overtone. The length of the string is $10\ cm$ and maximum amplitude of vibration of particles of the string is $2\ mm$ . Then the amplitude of the particle at $9\ cm$ from the open end is
A
$\sqrt 3\ mm$
B
$\sqrt 2\ mm$
C
$\frac{{\sqrt 3 }}{2}$
D
None of these
Solution

Second overtone $\Rightarrow 5$ th harmonic
So, $\lambda=\frac{4 L}{5}=8 \mathrm{\,cm}$
$\mathrm{A}_{\mathrm{s}}=(2 \mathrm{\,mm}) \sin (\mathrm{kx})=(2 \mathrm{\,mm}) \sin \left(\frac{2 \pi}{\lambda} x\right)$
$=(2 \mathrm{\,mm}) \sin \left(\frac{2 \pi}{8 \mathrm{\,cm}} \times 1 \mathrm{\,cm}\right)$
$=(2 \mathrm{\,mm}) \sin \left(\frac{\pi}{4}\right)=\sqrt{2} \mathrm{\,mm}$
Standard 11
Physics
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