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JEE Main 20199 AprilMorning Shift

Exam: JEE Main
Year: 2019
Date: 9 April
Shift: Morning Shift
Subject: Physics
Chapter: Waves and Sound

JEE Main 2019 · 9 April · Morning Shift · Physics · Waves and Sound

A string is clamped at both the ends and it is vibrating in its 4 ^...

A string is clamped at both the ends and it is vibrating in its

{4}^{th}

harmonic. The equation of the stationary wave is

y = 0.3\sin \left(0.157x\right)\cos ( 200\pit )

. The length of the string is
(All quantities are in

SI

units.)

Options

A $20m$
B $60m$
C $40m$
D $80m$

Correct answer

D. $80m$

Step-by-step solution

From the equation,

k = 0.157

\dfrac{2\pi}{\lambda} = 0.157

\lambda = 40m

But, length of the wire in

{4}^{th}

harmonic,

l = 4 \times \dfrac{\lambda}{2} = 2\lambda = 80m

.

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