If a number of sine waves with modulation indices $n_1, n_2, n_3, \dots$ modulate a carrier wave, then the total modulation index $(n)$ of the wave is:

Which of the following is a man-made signal?

$A$ sinusoidal carrier voltage of frequency $1.5 \, MHz$ and amplitude $50 \, V$ is amplitude modulated by a sinusoidal voltage of frequency $10 \, kHz$ producing $50 \%$ modulation. The lower and upper side-band frequencies in $kHz$ are:

$A$ transmitting antenna is at a height of $50 \ m$ and the receiving antenna is at a height of $5 \ m$. What is the maximum communication range in $km$? (Take $R = 6400 \ km$)

Given below are two statements:
Statement-$I$: $A$ speech signal of $2 \, kHz$ is used to modulate a carrier signal of $1 \, MHz$. The bandwidth requirement for the signal is $4 \, kHz$.
Statement-$II$: The sideband frequencies are $1002 \, kHz$ and $998 \, kHz$.
In the light of the above statements,choose the correct answer from the options given below:

The process of superimposing low-frequency signals onto high-frequency carrier waves is called ..........