You are driving down the road heading north at 15 m/s. An ambulance is driving in the opposite direction (south) towards you at 25 m/s. If the ambulance's siren emits sound at a frequency of 2 kHz, what frequency do you hear? Assume that the speed of sound is 340 m/s. a. 1780 Hz b. 1945 Hz c. 2254 Hz d. 2063 Hz e. 2000 Hz

The frequency of the siren heard by the driver is approximately 2254Hz.

Hence, Option C) 2254Hz is the correct answer.

Given the data in the question;

Frequency heard by observer;

To find the frequency heard by the observer, we Doppler Effect Equation:

Where is the observed frequency, is the actual frequency, is the velocity of sound, is the velocity of the observer and is the velocity of the source.

We substitute our given values into the equation

The frequency of the siren heard by the driver is approximately 2254Hz.

Hence, Option C) 2254Hz is the correct answer.

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d. 2063 Hz

Explanation:

Given that the source of the sound (the ambulance) is heading towards the observer, we have;

fL= (v ± vL/v ± vS) fS

Where;

v = speed of sound = 340 m/s

vL = velocity of the listener = 15 m/s

vS = velocity of the source = 25 m/s

fS = frequency of source = 2 kHz

Since the source is moving towards the observer we subtract;

Substituting values;

fL = (340 - 15/340 - 25)2 *10^3

fL = 2063Hz

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