An ambulance is generating a siren sound at a frequency of $2,400 \mathrm{~Hz}$. The speed of sound is $345.0 \mathrm{~m} / \mathrm{s}$. If the ambulance is traveling at a velocity of $24.00 \mathrm{~m} / \mathrm{s}$ toward the stationary observer, then what is the frequency of the siren perceived by the observer?
A) $2,525 \mathrm{~Hz}$
B) $2,480 \mathrm{~Hz}$
C) $2,500 \mathrm{~Hz}$
D) $2,540 \mathrm{~Hz}$
E) $2,579 \mathrm{~Hz}$

Question

Quizplus · Accepted Answer

The frequency perceived by the observer can be calculated using the formula for the Doppler effect: $f' = f \frac{v + v_o}{v - v_s}$, where $f'$ is the perceived frequency, $f$ is the source frequency, $v$ is the speed of sound, $v_o$ is the observer's velocity (0 in this case since the observer is stationary), and $v_s$ is the source's velocity towards the observer. Plugging in the given values: $f' = 2400 \frac{345.0}{345.0 - 24.00} = 2400 \times \frac{345.0}{321.0} \approx 2579 \mathrm{~Hz}$.

An Ambulance Is Generating a Siren Sound at a Frequency 2,400 Hz2,400 \mathrm{~Hz}2,400 Hz

An Ambulance Is Generating a Siren Sound at a Frequency $2,400 \mathrm{~Hz}$