1. Jane waits on a railroad platform while two trains approach from the same direction at equal speeds of 11.90 m/s. Both trains are blowing their whistles (which have the same frequency), and one train is some distance behind the other. After the first train passes Jane but before the second train passes her, she hears beats of frequency 6.50 Hz. What is the frequency of the train whistles?
2. Two point sources are in phase and emit a 406 Hz tone. What is the phase difference at a point that is 2.0 m from one source and 9.0 m from the other? (Take the air temperature to be 20°C.) in rad?