For a plane electromagnetic wave,which of the following quantities has an average value of zero?

The electric field part of an electromagnetic wave in a medium is represented by $E_x=0, E_y=2.5 \frac{N}{C} \cos \left[ (2\pi \times 10^6 \frac{rad}{s})t - (\pi \times 10^{-2} \frac{rad}{m})x \right]$,and $E_z=0$. The wave is

Electromagnetic waves of frequency $8.196 \times 10^6 \ Hz$ are propagating from a source. What is the wavelength of these electromagnetic waves in $cm$?

The electric field in a plane electromagnetic wave is given by $\overrightarrow{E} = 200 \cos \left[ (0.5 \times 10^{3} \text{ m}^{-1}) x - (1.5 \times 10^{11} \text{ rad/s}) t \right] \hat{j} \text{ V/m}$. If this wave falls normally on a perfectly reflecting surface having an area of $100 \text{ cm}^{2}$,and the radiation pressure exerted by the electromagnetic wave on the surface is $\frac{x}{10^{9}} \text{ N/m}^{2}$,find the value of $x$.

On a particular day,the sun delivers an average power of $\left(\frac{6}{\pi} \times 10^3\right) \frac{W}{m^2}$ to the top of Earth's atmosphere. Find the amplitude of the magnetic field for the electromagnetic waves above the atmosphere. (Take $\mu_0 = 4\pi \times 10^{-7} \text{ SI units}$)

The magnetic field of a plane electromagnetic wave is given by $B = (400 \ \mu T) \sin [ (4.0 \times 10^{15} \ s^{-1}) (t - \frac{x}{c}) ]$. The average energy density corresponding to the electric field is: