Question

A sound wave is propagating through a medium following an adiabatic process . Imagine that after some time, it starts following an isothermal process. ($V_{iso}$ is the speed of sound when it follows isothermal process and $V_{ad}$ is the speed of sound when it follows adiabatic process). Then

• A. $V_{ad}<V_{iso}$
• B. $V_{ad}=V_{iso}$
• C. $V_{ad}>V_{iso}$
• D. None of these

Answer 1

The correct option is C $V_{ad}>V_{iso}$

From formula for speed of sound,
$V_{ad}=\sqrt{\frac{\gamma P}{\rho }}$ and $V_{iso}=\sqrt{\frac{P}{\rho }}$
$\Rightarrow V_{ad}=\sqrt{\gamma }\times V_{iso}$
So, $V_{ad}>V_{iso}$
[Because $\gamma$ is a positive value which is greater than 1]