How are microwaves produced?

The speed of an electromagnetic wave in a vacuum depends upon the source of radiation.

$A$ radio receiver antenna that is $4 \, m$ long is oriented along the direction of the electromagnetic wave and it receives a signal of intensity $8 \times 10^{-16} \, W/m^2$. The maximum instantaneous potential difference across the two ends of the antenna is (in $ \, \mu V$)

Given below are two statements: one is labelled as Assertion $(A)$ and other is labelled as Reason $(R).$
Assertion $(A):$ Electromagnetic waves carry energy but not momentum.
Reason $(R):$ Mass of a photon is zero.
In the light of the above statements,choose the most appropriate answer from the options given below:

If the magnetic field of a light wave oscillates parallel to the $y-$ axis and is given by $B_y = B_m \sin(kz - \omega t)$,the direction of wave travel and the axis along which the electric vector oscillates are:

In a plane electromagnetic wave,the electric field oscillates with a frequency $2 \times 10^{10} \,s^{-1}$ and amplitude $40 \,Vm^{-1}$. The energy density due to the electric field is (given $\varepsilon_0 = 8.85 \times 10^{-12} \,Fm^{-1}$):