Medium INTEGER +4 / -1 PYQ · JEE Mains 2021

Two waves are simultaneously passing through a string and their equations are :

y1 = A1 sin k(x $-$ vt), y2 = A2 sin k(x $-$ vt + x0). Given amplitudes A1 = 12 mm and A2 = 5 mm, x0 = 3.5 cm and wave number k = 6.28 cm$-$1. The amplitude of resulting wave will be ................ mm.

Answer (integer) 7

Solution

y<sub>1</sub> = A<sub>1</sub> sin k(x $-$ vt)<br><br>y<sub>1</sub> = 12 sin 6.28 (x $-$ vt)<br><br>y<sub>2</sub> = 5 sin 6.28 (x $-$ vt + 3.5)<br><br>$\Delta \phi = {{2\pi } \over \lambda }(\Delta x)$<br><br>$= K(\Delta x)$<br><br>$= 6.28 \times 3.5 = {7 \over 2} \times 2\pi = 7\pi$<br><br>${A_{net}} = \sqrt {A_1^2 + A_2^2 + 2{A_1}{A_2}\cos \phi }$<br><br>${A_{net}} = \sqrt {{{(12)}^2} + {{(5)}^2} + 2(12)(5)\cos (7\pi )}$<br><br>$= \sqrt {144 + 25 - 120}$

About this question

Subject: Physics · Chapter: Waves · Topic: Wave Motion and Types

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