The height of an antenna is $500 \ m$. Its range is ........ $km$. (Radius of the Earth is $6400 \ km$)

$A$ message signal of frequency $3\,kHz$ is used to modulate a carrier signal of frequency $1.5\,MHz$. The bandwidth of the amplitude modulated wave is

The transmission of $UHF$ range frequencies is done by.........

Broadcasting antennas are generally

Which of the following statements is $NOT$ true regarding communication through optical fibers?

The waves which are reflected back to the earth by the ionosphere are: