The electric field and magnetic field associated with an electromagnetic $(e.m.)$ wave,propagating along the $-z$ axis,can be represented by:

Assertion : Radio waves can be polarised.
Reason : Sound waves in air are longitudinal in nature.

Which of the following statements is false regarding the properties of electromagnetic waves?

$A$ plane electromagnetic $(EM)$ wave is propagating along the $x$-direction. It has a wavelength of $4 \text{ mm}$. If the electric field is in the $y$-direction with a maximum magnitude of $60 \text{ Vm}^{-1}$,the equation for the magnetic field is:

$A$ plane electromagnetic wave of frequency $20\, MHz$ propagates in free space along the $x$-direction. At a particular space and time, $\overrightarrow{E} = 6.6 \hat{j} \, V/m$. What is $\overrightarrow{B}$ at this point?

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 $x$.