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BITSAT 2012
Exam
BITSAT
Year
2012
Subject
Physics
Chapter
Waves and Sound

BITSAT 2012 · Physics · Waves and Sound

The transverse displacement y(x, t) of a wave on a string is given...

The transverse displacement y(x,t)y(x, t) of a wave on a string is given by y(x,t)=e−(ax2+bt2+2aby(x, t)=e^{-\left(a x^{2}+b t^{2}+2 \sqrt{a b}\right.} xt )) This represents a

Options

  1. Awave moving in −x-x direction, speed ba\sqrt{\frac{b}{a}}
  2. Bstanding wave of frequency b\sqrt{b}
  3. Cstanding wave of frequency 1b\frac{1}{\sqrt{b}}
  4. Dwave moving in +x+x direction, speed ab\sqrt{\frac{a}{b}}

Correct answer

A. wave moving in −x-x direction, speed ba\sqrt{\frac{b}{a}}

Step-by-step solution

y(x,t)=e−(ax2+bt2+2abxt)=e−(ax+bt)2y(x, t)=e^{-\left(a x^{2}+b t^{2}+2 \sqrt{a b} x t\right)}=e^{-(\sqrt{a x}+\sqrt{b t})^{2}} It is a function of type y=f(ωt+kx)∴y(x,t)y=f(\omega t+k x)\therefore y(x, t) represents wave travelling along −x-x direction.  Speed of wave =ωk=ba=ba\text{ Speed of wave }=\frac{\omega}{k}=\frac{\sqrt{b}}{\sqrt{a}}=\sqrt{\frac{b}{a}}
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