Archive
3rd of March 2017
Physics
Q:

Why and how Laplace corrected Newton's formula for velocity of sound in gas?

Riya Sunil - CBSE - Class XI Science

Thursday, March 02, 2017 at 20:19:PM

A:

Hi Riya!

Its nice to see you again!

Newtons formula for velocity of sound in gas states that sound travels in the form of rarefaction and compression.
Heat is evolved in rarefaction and heat is lost during the compression of the sound and the transfer of the heat depends on the gradient of the temperature (from hotter body to the cooler body). Therefore the net transfer of heat remains same within the system and that propagation of sound in gas is an isothermal process.
These assumptions, with the help of iso-thermal bulk modulus yielded the velocity of sound as 279 m/s.

But, the practical value of velocity of sound in gas is something else that is 331 or 332 m/s.
So Laplace corrected it with his theory that the process of heat transfer during the propagation of sound in gas is an adiabatic process i.e heat does not enters nor leaves the system concerned.
And Laplace theory with the help of adiabatic bulk modulus yielded accurate value of velocity of sund in gas which is 331 or 332 m/s.

Hope this helped!
See you again,be a topper forever!!!

Friday, March 03, 2017 at 18:26:PM