In amplitude modulation,the amplitude of the $.......$ wave varies in proportion to the instantaneous value of the $.......$ wave.

In an amplitude modulation,a modulating signal having amplitude of $X$ Volt is superimposed with a carrier signal of amplitude $Y$ Volt in the first case. In the second case,the same modulating signal is superimposed with a different carrier signal of amplitude $2Y$ Volt. The ratio of the modulation index in the two cases respectively will be:

The sound produced by a tuning fork is a/an .....

What should be the height of a transmission antenna (in $m$) to cover a range of $128 \, km$?

$A$ $TV$ transmitter has a range of $50 \ km$. The height of the $TV$ transmitter is $......$ (Radius of the earth $R_e = 6.4 \times 10^6 \ m$) (in $m$)

The characteristic impedance of a coaxial cable is typically in the range of ..........