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 frequency of a carrier wave is $1 MHz$. It is modulated by a wave of frequency $10 kHz$. If their amplitudes are $10 V$ and $0.5 V$ respectively,what are the modulation index and the frequencies of the $USB$ and $LSB$?

An information signal of frequency $10 \text{ kHz}$ is modulated with a carrier wave of frequency $3.61 \text{ MHz}$. The upper sideband and lower sideband frequencies are:

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

The process of superimposing a signal frequency onto a carrier wave is known as .......

The refractive index of the ionosphere: