Light waves are which type of waves?

What are called non-mechanical waves? Give its examples.

If a source is transmitting electromagnetic waves of frequency $8.196 \times 10^{6} \ Hz$,then the wavelength of the $EM$ waves transmitted from the source will be . . . . . . . (in $cm$)

If a plane electromagnetic wave has electric field oscillations of frequency $3 \text{ GHz}$, then the wavelength of the wave is (speed of light in vacuum $= 3 \times 10^8 \text{ m/s}$) (in $\text{ m}$)

$A$ point source of electromagnetic radiation has an average power output of $800\,W$. The maximum value of the electric field at a distance of $3.5\,m$ from the source will be.....$V/m$.

Which of the following is/are the property/properties of a monochromatic electromagnetic wave propagating in the free space?
$1$. Electric and magnetic fields will have a phase difference $\frac{\pi}{2}$.
$2$. The energy of the wave is distributed equally between electric and magnetic fields.
$3$. The pressure exerted by the wave is the product of its speed and energy density.
$4$. The speed of the wave is equal to the ratio of the magnetic field to the electric field.