The height of a $TV$ transmitter antenna is $100 \ m$. What is the area covered by the transmitter for broadcasting? $(R = 6.4 \times 10^{6} \ m)$

An amplitude modulated signal consists of a message signal of frequency $1 \text{ kHz}$ and peak voltage of $5 \text{ V}$,modulating a carrier frequency of $1 \text{ MHz}$ and peak voltage of $15 \text{ V}$. The correct description of this signal is

At a particular station,the $TV$ transmission tower has a height of $100\,m$. To triple its coverage range,the height of the tower should be increased to ......$m$.

Mean optical power launched into an $8 \ km$ fibre is $120 \ \mu W$ and mean output power is $4 \ \mu W$,then the overall attenuation is ....... $dB$ (Given $\log 30 = 1.477$)

The mathematical form of an $AM$ wave is given by $e = 50 (1 + 0.5 \sin (2\pi \times 5 \times 10^{3}) t) \sin (31.4 \times 10^{6}) t \, V$. To generate this $AM$ wave,the amplitudes of the carrier wave and the modulating wave must be,respectively,....... and ....... .

$A$ carrier wave of peak voltage $14\,V$ is used for transmitting a message signal. The peak voltage of the modulating signal required to achieve a modulation index of $80\%$ will be.......$V$