$A$ wave is represented as $e = 10 \sin(10^8 t + 6 \sin(1250 t))$. The modulation index is:

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

$A$ basic communication system consists of:
$(A)$ Transmitter $(B)$ Information source $(C)$ User of information $(D)$ Channel $(E)$ Receiver
Choose the correct sequence in which these are arranged in a basic communication system.

The height of a $T.V.$ tower is $75 \ m$. What is the maximum distance in $km$ up to which $T.V.$ transmission can be received (in $.98$)? (Radius of the Earth $= 6.4 \times 10^6 \ m$).

Define the following terms:
$(a)$ Ground waves
$(b)$ Trade winds

In an $AM$ wave,the frequencies of $LSB$ and $USB$ are $2.99 \ MHz$ and $3.01 \ MHz$ respectively. The carrier frequency is ....... and the modulating frequency is .......