Topic: Electromagnetics
A plane wave propagating in the dielectric medium has an electric field given as $E_{x}=E_{0}cos(2.6\times10^{10}t-100~z)$. The phase velocity of plane wave is
- A. $10^{6}m/sec$
- B. $2.6\times10^{8}m/sec$
- C. $3.0\times10^{8}m/sec$
- D. $4.0\times10^{8}m/sec$
Answer: B. $2.6\times10^{8}m/sec$
Explanation: $E_{x}=E_{0}cos(2.6\times10^{10}t-100z)$. Comparing it with standard equation $E_{x}=E_{o}cos(\omega t-\beta z)$, $\omega=2.6\times10^{10}rad/sec.$, $\beta=100~rad/m$. Phase velocity, $v_{p}=\frac{\omega}{\beta}=\frac{2.6\times10^{10}}{100} = 2.6\times10^{8}m/sec$.