A sound wave travelling through air can be represented by alternate regions of high and low pressure along the direction of propagation.
(i) Define (a) compression and (b) rarefaction with reference to a longitudinal sound wave.
(ii) Draw a neat, labelled sketch of one complete longitudinal sound wave in air and mark the following on it: two successive compressions (C1 and C2), two successive rarefactions (R1 and R2) and one wavelength (λ).
(iii) Explain clearly how the wavelength is measured on your sketch and state why this distance remains constant for a given source and medium.