A radio wave of frequency propagates through a uniform plasma layer whose electron…

PHYSICS · Multi-part · Fermi University Physics · Plasma Physics · Waves in plasmas · Waves in plasmas

Plasma Physics, Ch Plasma oscillations and light in an unmagnetised plasma

Problem

A radio wave of frequency

f = 12\,\mathrm{MHz}

propagates through a uniform plasma layer whose electron plasma frequency is

f_{pe} = 8.0\,\mathrm{MHz}

(so

f = 1.5f_{pe}

). ((a)) Find the refractive index

n

. ((b)) Find the phase velocity

v_p

and the group velocity

v_g

. ((c)) Verify that

v_pv_g = c^2

, and explain why

v_p > c

does not violate relativity.