Question

Velocity of sound in oxygen at NTP is v. The velocity of sound in helium at NTP should be

• A. $2v$
• B. $4v$
• C. $2\sqrt{2}v$
• D. $none$

Answer 1

Answer: (C)

$2\sqrt{2}v$

$v\propto \frac{1}{\sqrt{M_{gas}}}$

Here, v is the velocity of sound in the medium, $M_{gas}$ is the molecular/atomic weight of the gas.

Therefore,

$\frac{v_{He}}{v_{O_2}}=\sqrt{\frac{M_{O_2}}{M_{He}}}=\sqrt{\frac{32}{4}}=\sqrt{8}=2\sqrt{2}$

Option "C" is correct.