The radius of the Earth is $6400 \text{ km}$. If the height of the antenna is $500 \text{ m}$, then its range is: (in $\text{ km}$)

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

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:

If the height of transmitting and receiving antennas are $80\,m$ each,the maximum line of sight distance will be $..............\,km$. Given: Earth's radius $= 6.4 \times 10^6\,m$.

$A$ square wave of the modulating signal is shown in the figure. The carrier wave is given by $C(t) = 5 \sin(8\pi t) \text{ V}$. The modulation index is:

This question has Statement-$1$ and Statement-$2$. Of the four choices given after the statements,choose the one that best describes the two statements.
Statement-$1$: Sky wave signals are used for long-distance radio communication. These signals are,in general,less stable than ground wave signals.
Statement-$2$: The state of the ionosphere varies from hour to hour,day to day,and season to season.