Two tuning forks produce audible beats when sounded together. Fork X has a fixed frequency of 256 Hz, while fork Y has a frequency close to it.
Answer the following questions related to the phenomenon:
(i) Define a beat and state the condition under which beats are heard.
(ii) Explain, without using any formula, how the phase relation between the two waves leads to periodic waxing and waning of sound intensity.
(iii) If fork Y is set into vibration and then moved steadily towards a stationary listener, describe qualitatively how the beat frequency will change. Give reason for your answer.
(iv) State one situation in which the beats originally heard may completely disappear even though both forks are still vibrating.