Q6: When an ambulance approaches a stationary man, the equency of siren seems higher than that when the ambulance is at rest. The man hears a lowered frequency of siren when the ambulance leaves him. Explain the phenomenon. [100 words] (5 marks) On a long straight road, a cyclist is travelling at 19,: = 10 m/s and an oncoming motorbike is travelling at vm = 20 m/ s. If the motorcycle honks at a frequency of f : 600 Hz all the time and the speed of sound is 125 = 340 m/s, nd the frequency heard by cyclist 0\") before and after he meets the motorcycle. (5 marks) usivc Useful formula: f ' = f. Please determine the signs (i.e. the positive or negative signs) when you use this formula.| usivm