The size of the antenna required for a carrier wave of frequency $3 \text{ MHz}$ is: (in $\text{ m}$)

Ground waves are polarized in which direction?

$A$ basic communication system consists of:
$(a)$ Transmitter
$(b)$ Information source
$(c)$ User of information
$(d)$ Channel
$(e)$ Receiver
The correct sequence of the arrangement is:

Match List-$I$ with List-$II$:

List-$I$	List-$II$
$A$. $AM$ Broadcast	$I$. $88-108\,MHz$
$B$. $FM$ Broadcast	$II$. $540-1600\,kHz$
$C$. Television	$III$. $3.7-4.2\,GHz$
$D$. Satellite Communication	$IV$. $54-890\,MHz$

Choose the correct answer from the options given below:

Only $2 \%$ of the optical source frequency is the available channel bandwidth for an optical communication system operating at $1000 \,nm$. If an audio signal requires a bandwidth of $8 \,kHz$,how many channels can be accommodated for transmission?

In short wave communication, waves of which of the following frequencies will be reflected back by the ionospheric layer having an electron density of $10^{11} \text{ per } m^3$ (in $\text{ MHz}$)?