The 440Hz tuning fork is used with a resonating column to determine the velocity of sound in helium gas.

Question

If the spacing between resonance are 110 cm, what is the velocity of sound in He?

 

ans. 970m/s

 

ps. How can I get the answer? Thx! 

Answer 1

Just a quick note that this is true as long as the column of air is open at both ends.  If it were closed at one end, the spacing between resonances (which are all presumed to be the fundamental harmonic for that length of column) would be the wavelength divided by 4.

This is because the length of a pipe open at both ends is half of the total fundamental wavelength; while, for a pipe closed at one end, it is 1/4 the total fundamental wavelength

Answer 2

Hi Nic

In an air column the spacing between resonance is wave length /2

 

So wave length = 220 cm = 2.2m

 

Then Velocity = frequency * wave length

 

So Velocity of wave = 440 * 2.2 = 968m/s