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.

Plasma Frequency Calculator
Electron Number Density
Electronic Charge
Permittivity of Vaccum
Mass of Electron
Plasma Frequency: {{plasmaFrequencyResult() | number:4}}

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