What is a transducer?

In amplitude modulation,the sinusoidal carrier frequency is denoted by $\omega_c$ and the signal frequency is denoted by $\omega_m$. The bandwidth of the signal is such that $\omega_m << \omega_c$. Which of the following frequencies is not contained in the modulated wave?

The mathematical form of an $AM$ wave is given by $e = 50 (1 + 0.5 \sin(2\pi \times 5 \times 10^{3} t)) \sin(31.4 \times 10^{6} t) \text{ volts}$. Which of the following frequencies is absent in the given $AM$ wave?

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

In the process of modulation,........

The maximum distance up to which $TV$ transmission from a $TV$ tower of height $h$ can be received is proportional to