iran-konkur 2016 Q194

iran-konkur · Other · konkur-riazi_1395_specialized Not Maths
194. A sound source moving with speed $\dfrac{1}{n}$ of the speed of sound approaches a stationary listener, and continues along the same path at the same speed. If in the first case the frequency heard by the listener is $\Delta f$ and in the second case the frequency of the source decreases, and the frequency heard by the listener is $\Delta f'$, the ratio $\dfrac{\Delta f}{\Delta f'}$ is:
  • [(1)] $1$ (2) $\dfrac{n-1}{n}$ (3) $\dfrac{n+1}{n-1}$ (4) $\dfrac{1}{n+1}$

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\textbf{194.} A sound source moving with speed $\dfrac{1}{n}$ of the speed of sound approaches a stationary listener, and continues along the same path at the same speed. If in the first case the frequency heard by the listener is $\Delta f$ and in the second case the frequency of the source decreases, and the frequency heard by the listener is $\Delta f'$, the ratio $\dfrac{\Delta f}{\Delta f'}$ is:

\begin{itemize}
\item[(1)] $1$ \quad (2) $\dfrac{n-1}{n}$ \quad (3) $\dfrac{n+1}{n-1}$ \quad (4) $\dfrac{1}{n+1}$
\end{itemize}



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