Teaching UP PGT Mock Test Series 2024 Physical Sciences Electromagnetic Theory Dispersion Relations in Plasma
Suppose that there is a dispersive medium whose refractive index depends on the wavelength as given by \(n(\lambda)=n_0+\frac{a}{\lambda^2}-\frac{b}{\lambda^4}\). The value of 𝜆 at which the group and phase velocities would be the same, is:
1
\( \sqrt{\frac{2 b}{a}} \)
2
\( \sqrt{\frac{b}{2 a}} \)
3
\( \sqrt{\frac{3 b}{a}} \)
4
\( \ \sqrt{\frac{b}{3 a}} \)