State what is meant by amplitude modulation (AM).
A sinusoidal radio carrier wave of frequency $900\,\text{kHz}$ and unmodulated amplitude measured to be $4.0\,\text{V}$ is amplitude modulated by a signal of frequency $5.0\,\text{kHz}$. For the amplitude modulated wave, determine the wavelength.
Describe how the amplitude varies for the amplitude modulated wave.
State the bandwidth.
Communication is sometimes carried out using satellites in geostationary orbits with a period of rotation about the Earth of $24$ hours. State two other features, apart from the period, of a geostationary orbit.
Suggest why frequencies of the order of gigahertz are chosen for satellite communication.
Suggest why the uplink frequency to the satellite differs from the downlink frequency.