Question

The speed of sound in oxygen (O2) at a certain temperature is 460m/s. The speed of sound in helium (He) at the same temperature will be (assume both gases to be ideal).

(a) 460m/s

(b) 500m/s

(c) 650m/s

(d) 1420m/s

This question was addressed to me at a job interview.

This question is from Longitudinal Waves topic in portion Waves of Engineering Physics I

Answer 1

Right choice is (d) 1420m/s

The explanation is: vHe/v(O2) = √(γHe/γ(O2) ×M(O2)/MHe)=√((5/3)/(7/5)×32/4)=√(200/21)

=√9.52=3.086

vHe=3.086v(O2)=3.086×460=1420m/s.