Which of the following frequencies does not belong to the $FM$ broadcast band (in $,MHz$)?

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

The process of retrieval of information from the carrier wave is known as:

While tuning in a certain broadcast station with a receiver,we are actually

An amplitude modulated wave is represented by the expression $v_{m}=5(1+0.6 \cos 6280 t) \sin (211 \times 10^{4} t) \; V$. The minimum and maximum amplitudes of the amplitude modulated wave are,respectively:

$A$ telephonic communication service is working at a carrier frequency of $20 GHz$. Only $20 \%$ of it is utilized for transmission. If each channel requires a bandwidth of $5 kHz$,then the number of telephonic channels that can be transmitted simultaneously are