An ambulance is traveling north at 48.4 m/s, approaching a car that is also traveling north at 28 m/s. The ambulance driver hears his siren at a frequency of 620 Hz. Ambulance 48.4 m/s 28 m/s Car What is the wavelength at any position in front of the ambulance for the sound from the ambulance’s siren? The velocity of sound in air is 343 m/s. Answer in units of m.

Explanation:

For any point stationary in front of ambulance , the ambulance is approaching the point . In this way the case is similar to source of sound approaching the observer. The doppler's effect can be applied to know the apparent frequency.

velocity of sound V = 343 m /s

speed of source Vs = 48.4

observer is stationary.

apparent frequency = real frequency x V / ( V - Vs )

= 620 x 343 / ( 343 - 48.4 )

= 722 Hz approx.