Q. A plane electromagnetic wave of frequency 20 MHz travels in free space along the $+x$ direction. At a particular point in space and time, the electric field vector of the wave is $E_y=9.3\ \mathrm{Vm^{-1}}$. Then, the magnetic field vector of the wave at that point is
A) $B_z=6.2\times10^{-8}$ T
B) $B_z=3.1\times10^{-8}$ T
C) $B_z=1.55\times10^{-8}$ T
D) $B_z=9.3\times10^{-8}$ T
Explanation
[Solution by Dr. Abubacker] $B=\frac Ec=\frac{9.3}{3\times10^8}=3.1\times10^{-8}$ T. With $\vec E$ along $y$ and propagation along $+x$, $\vec B$ is along $+z$. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.