State what is meant by the principle of superposition.
A transmitter sends microwaves through air towards a metal plate, as shown in Fig. 4.1. The microwaves have a wavelength of $0.040\text{ m}$. A stationary wave is formed between the transmitter and the plate. Explain the role of the metal plate.
Calculate the frequency of the microwaves, in $\text{GHz}$.
A microwave receiver starts at position X where it measures an intensity minimum. The receiver is then slowly moved directly towards the plate, away from X. Determine the shortest distance from X at which the receiver detects another intensity minimum.
Determine the number of intensity maxima the receiver detects as it moves from X to a point $9.1\text{ cm}$ from X.
Determine the shortest distance from X when the receiver detects another intensity minimum.
Determine the number of intensity maxima the receiver detects as it moves from X to a point $9.1\,\text{cm}$ from X.