The relationship between the maximum electron density $(N_{max})$ of the ionosphere and the critical frequency $(f_c)$ is given by:

The process of superimposing a signal frequency onto a carrier wave is known as .......

Which of the following statements is $NOT$ correct?

An amplitude modulated wave is represented by $C_{m}(t)=10(1+0.2 \cos 12560 t) \sin (111 \times 10^{4} t)$ volts. The modulating frequency in $kHz$ will be ........... .

An antenna uses electromagnetic waves of frequency $5 \text{ MHz}$. For proper working,the size of the antenna should be:

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?