The attenuation in optical fibre is mainly due to

Which types of communication modes are used for the propagation of radio waves from one place to another?

For $100\%$ modulation,what should be the value of the minimum amplitude $(E_{min})$ of the modulated wave?

The electron density of the ionospheric layer is $10^{11} \ m^{-3}$. Communication waves of frequency up to $f_c$ $MHz$ will be reflected by the ionospheric layer. Find $f_c$.

Which of the following options is $NOT$ correct? We need modulation for:

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 ......$m$.