All electromagnetic waves transport energy in the negative $z$ direction. At a certain point and time,the direction of the electric field of the wave is along the positive $y$ direction. What will be the direction of the magnetic field of the wave at that point and instant?

How is the average energy density in an electromagnetic wave related to the magnetic field?

An electromagnetic wave travels in free space along the $x$-direction. At a particular point in space and time, $\vec{B} = 2 \times 10^{-7} \hat{j} \text{ T}$ is associated with this wave. The value of corresponding electric field $\vec{E}$ at this point is . . . . . . $V$/m. (in $\hat{k}$)

The electron density of $E, F_1,$ and $F_2$ layers of the ionosphere is $4 \times 10^{11} \, m^{-3}, 9 \times 10^{11} \, m^{-3},$ and $16 \times 10^{11} \, m^{-3}$ respectively. What is the ratio of the critical frequencies for the reflection of radio waves?

An electron is constrained to move along the $y$-axis with a speed of $0.1 c$ ($c$ is the speed of light) in the presence of an electromagnetic wave,whose electric field is $\overrightarrow{E} = 30 \hat{j} \sin(1.5 \times 10^7 t - 5 \times 10^{-2} x) \, V/m$. The maximum magnetic force experienced by the electron will be: (given $c = 3 \times 10^8 \, m/s$ and electron charge $q = 1.6 \times 10^{-19} \, C$)

The electric field component of an electromagnetic wave in vacuum is given as $\vec E = 3\cos(1.8y + 5.4 \times 10^8 t)\hat i$. Its direction of propagation and wavelength are: