(a(i))[1]
State what is meant by a progressive wave.
(a(ii))[2]
State expressions, in terms of some or all of $f$, $\lambda$ and $n$, for: the distance travelled by a wavefront in time $t$; and time $t$.
(a(iii))[1]
Use your answers in (ii) to find an expression for the wave speed $v$ in terms of $f$ and $\lambda$.
(b(i))[2]
Calculate the frequency, in GHz, of the microwaves.
(b(ii))[1]
Show that the difference in path lengths $XQ$ and $YQ$ is $6\,\text{cm}$.
(b(iii))[3]
State and explain what can be concluded about the intensity of the microwaves at point $Q$.
(b(iv))[2]
A microwave detector is placed at $P$ and linked to a cathode-ray oscilloscope (CRO). The CRO settings are adjusted so that a waveform appears on the screen. Describe how the amplitude of the waveform changes as the detector is moved from $P$ to $Q$.