The frequency at which the plasma oscillation occurs is called the plasma frequency which can be calculated using this simple physics calculator based on electron number density, electronic charge, permittivity of vacuum and mass of electron.

Formula

ωp=√((ne*e2)/(εo*me))

Where,

ωp = Plasma angular Frequency

ne = Electron number density

e = Electronic charge

εo = Permittivity of vaccum

me = Mass of electron