VIT Engineering VIT Engineering Solved Paper-2009

  • question_answer
    When a wave traverses a medium, the displacement of a particle located at\[x\] at a time \[t\] is given by \[y=a\text{ }sin\left( bt-\text{c}x \right)\], where \[a\],\[b\]and\[c\] are constants of the wave, which of the following is a quantity with dimensions?

    A)  \[\frac{y}{a}\]                 

    B)  \[bt\]

    C)  \[cx\]                

    D)  \[\frac{b}{c}\]

    Correct Answer: D

    Solution :

    Given,  \[y=a\,\sin (bt-cx)\] Comparing the given equation with general wave equation \[y=a\,\sin \,\,\left( \frac{2\pi t}{T}-\frac{2\pi x}{\lambda } \right)\] we get       \[b=\frac{2\pi }{T},\,c=\frac{2\pi }{\lambda }\] [a] Dimensions of \[\frac{y}{a}=\frac{metre}{metre}=\frac{[L]}{[L]}\] = Dimensionless [b] Dimensions of \[bt=\frac{2\pi }{T},\,t=\frac{[T]}{[T]}\] = Dimensionless [c] Dimensions of \[cx=\frac{2\pi }{\lambda }.x=\frac{[L]}{[L]}\] = Dimensionless [d] Dimensions of \[\frac{b}{c}={\frac{2\pi }{T}}/{\frac{2\pi }{\lambda }}\;\] \[=\lambda /T=[L{{T}^{-1}}]\] Thus, option  has dimensions.  


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