The frequency dependent dielectric constant of a material is given by \epsilon (\omega )=1+\frac{A}{{\omega }_{0}^{2}- {\omega }^{2}- i\omega \gamma } where A is a positive constant, {\omega }_{0} the resonant frequency and \gamma the damping coefficient. For an electromagnetic wave of angular frequency \omega \ll {\omega }_{0} which of the following is true? (Assume that \frac{\gamma }{{\omega }_{0}}\ll 1).

Plasma — CSIR Net PYQ (Question 1)

A Plasma previous-year question (PYQ) from Electromagnetism (CSIR Net). Read the question, check the correct answer, then practise the full topic.

Question 1 of 5 · 5.0 marks

The frequency dependent dielectric constant of a material is given by

ϵ (ω) = 1 + \frac{A}{ω _{0}^{2} - ω ^{2} - iω γ}

where

A

is a positive constant,

ω_{0}

the resonant frequency and

γ

the damping coefficient. For an electromagnetic wave of angular frequency

ω ≪ ω_{0}

which of the following is true? (Assume that

\frac{γ}{ω _{0}} ≪ 1

1There is negligible absorption of the wave
2The wave propagation is highly dispersive
3There is strong absorption of the electromagnetic wave
4The group velocity and the phase velocity will have opposite sign

Correct answer: Option 1

Practise all 5 Plasma questions with instant feedback.

Practise this topic →

About this question

This Plasma PYQ is part of the Electromagnetism section of CSIR Net. Browse more Plasma questions or join the PhysicsByAaryan live batch for full conceptual coverage.