i) At a factory, a noon whistle is sounding having a frequency of 451 Hz. As the car traveling at 84 km/h approaches the factory, the driver hears the whistle at frequency fi. Subsequent to driving past the factory, the driver hears frequency ff. Determine the change in frequency ff - fi heard by the driver? (Suppose a temperature of 20° C.)
ii) A source of sound waves having frequency 0.9 kHz is traveling via the air at 0.75 times the speed of sound.
(a) Determine the frequency of the sound received through a stationary observer when the source moves toward her?
(b) Now, the source moves away from the stationary observer. Determine the frequency of the sound received in the case?