They oscillate back and forth at the plasma frequency until the energy is lost in some kind of resistance or damping.

Interestingly the permittivity of this material, above the plasma frequency can be positive and less than one.

Certain metals near their plasma frequency, or metamaterials with negative parameters could fill this need.

Light of frequency above the plasma frequency is transmitted, because the electrons cannot respond fast enough to screen it.

The frequencies of the radio waves are below the plasma frequency of the interstellar medium.

Below the plasma frequency, the dielectric function is negative and the field cannot penetrate the sample.

Light with angular frequency below the plasma frequency will be totally reflected.

Above the plasma frequency the light waves can penetrate the sample.

If they talk to each other in low frequencies, it won't come through that blob because the plasma frequency is higher.

Classically only a single resonance is expected, centered at the plasma frequency .