Question

Recently astronomers have discovered a planet with water vapour in the habitable zone, called exoplanet K2-18B. It has an atmosphere, and the pressure is 5.2% more than that of the earth. If the ambient temperature is roughly the same as earth’s, what is the speed of sound there?

Answer 1

The speed of sound will be same as that of earth. 343 m/s at 20^oC.

The speed of sound does have an effect on pressure. But it has the same effect on density of the medium and ideally, these values cancel each other.

For general equation of state in classical mechanics, the speed of sound is given by

p is the pressure and is the density, which again is dependent on pressure for an ideal gas.

Even in the non- ideal case, pressure has a slight but negligible effect on the the speed of sound for a small pressure change of 5.2%..