Answer the following questions about the characteristics of sound waves.
(i) Define frequency and wavelength of a sound wave and state their SI units.
(ii) When a sound produced by a tuning fork travels from air into water, which of its characteristics—frequency, wavelength, speed, amplitude—change and which remain the same? Give reasons for each case.
(iii) A swimmer hears the same tuning fork while submerged in water. Will the pitch that the swimmer perceives be different from that heard by a listener in air? Explain your answer with proper reasoning.