(a)[1]
State what the wavelength of a progressive wave means.
(b)[2]
A cathode-ray oscilloscope (CRO) is being used to examine a sound wave. The CRO time-base is set to $2.5\,\text{ms cm}^{-1}$. Find the frequency of the sound wave.
(c(i))[1]
Show that the waves arriving at $C$ have a path difference of $6.4\,\text{m}$.
(c(ii))[2]
Explain why an intensity maximum is observed at point $C$.
(c(iii))[2]
Determine the difference between the times taken for sound to travel from the source to point $C$ along the two different paths.
(c(iv))[1]
The wavelength of the sound is increased gradually. Calculate the wavelength when the next intensity maximum is detected at point $C$.