In a communication system operating at a wavelength of $800\,nm,$ only one percent of the source frequency is available as signal bandwidth. The number of channels accommodated for transmitting $TV$ signals of bandwidth $6\,MHz$ is (Take velocity of light $c = 3 \times 10^8\,m/s$)

What is the modulation index of an over-modulated wave?

The intensity of a light pulse travelling along a communication channel decreases exponentially with distance $x$ according to the relation $I = I_0 e^{-\alpha x}$,where $I_0$ is the intensity at $x = 0$ and $\alpha$ is the attenuation constant. The attenuation in $dB/km$ for an optical fibre in which the intensity falls by $50$ percent over a distance of $50 \ km$ is

The total maximum transmitted power in amplitude modulation if the carrier output power is $1 \ kW$ is

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?

This question has Statement-$1$ and Statement-$2$. Of the four choices given after the statements,choose the one that best describes the two statements.
Statement-$1$: Sky wave signals are used for long-distance radio communication. These signals are,in general,less stable than ground wave signals.
Statement-$2$: The state of the ionosphere varies from hour to hour,day to day,and season to season.