For efficient transmission of sound waves of wavelength $\lambda$,the minimum length of the antenna should be.....

Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen,the frequency of the radio waves must be in the range:

$A$ carrier signal of frequency $1.5 MHz$ has an amplitude of $50 V$. It is amplitude modulated by a modulating wave of frequency $10 kHz$ with a modulation index of $50 \%$. What are the frequencies of the $LSB$ and $USB$?

$A$ transmitting antenna is kept on the surface of the earth. The minimum height of the receiving antenna required to receive the signal in line-of-sight at $4\,km$ distance from it is $x \times 10^{-2}\,m$. The value of $x$ is (Let radius of earth $R = 6400\,km$).

Which of the following is $NOT$ a reason for why we need modulation in communication systems?

Which of the following statements is $NOT$ true?