The siren on an ambulance is emitting a sound whose frequency is 2350 Hz. The sp

Question

The siren on an ambulance is emitting a sound whose frequency is 2350 Hz. The speed of sound is 343 m/s.

(a) If the ambulance is stationary and you (the "observer") are sitting in a parked car, what are the wavelength and the frequency of the sound you hear?

(b) Suppose that the ambulance is moving toward you at a speed of 26.9 m/s. Determine the wavelength and the frequency of the sound you hear.

(c) If the ambulance is moving toward you at a speed of 26.9 m/s and you are moving toward it at a speed of 15.0 m/s, find the wavelength and frequency of the sound you hear.

Explanation / Answer

n = 2350 Hz
c = n = 343 m/s

a )
= 343/ 2350 = 0.145 m .
n = 2350 Hz

b)
Source is moving and observer is at rest.
n’ = c n /(c-Vs) = 343 * 2350/ ( 343 – 26.9) = 2549.984 Hz
= 343/ 2549.984 = 0.134m

c)
Source and observer are moving toward each other
n’ = ( c + Vo) n /(c-Vs) = ( 343 + 15)* 2350 / ( 343 – 26.9)
n’ = 2661.499 Hz
= 343/ 2661.499 = 0.1288m
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