An antenna is placed in a dielectric medium of dielectric constant $6.25$. If the maximum size of the antenna is $5.0 \, mm$,what is the minimum frequency of the signal it can radiate in $GHz$? (Given $\mu_{r} = 1$ for the dielectric medium)

$A$ sinusoidal carrier voltage of frequency $1.5 \, MHz$ and amplitude $50 \, V$ is amplitude modulated by a sinusoidal voltage of frequency $10 \, kHz$ producing $50 \%$ modulation. The lower and upper side-band frequencies in $kHz$ are:

$A$ signal of $0.1 \, kW$ is transmitted in a cable. The attenuation of the cable is $-5 \, dB$ per $km$ and the cable length is $20 \, km$. The power received at the receiver is $10^{-x} \, W$. The value of $x$ is ....... .
$[\text{Gain in } dB = 10 \log_{10}(\frac{P_0}{P_i})]$

When the modulating frequency is doubled, the modulation index is halved and the modulating voltage remains constant, the modulation system is

The maximum and minimum voltage of an amplitude modulated signal are $60\,V$ and $20\,V$ respectively. The percentage modulation index will be $....\%$

If the maximum and minimum voltage of an $AM$ wave are $V_{max}$ and $V_{min}$,then the modulation index is given by: