The siren on an ambulance is emitting a sound whose frequency is 2517 Hz. The sp

Question

The siren on an ambulance is emitting a sound whose frequency is 2517 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 28.9 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 28.9 m/s and you are moving toward it at a speed of 13.1 m/s, find the wavelength and frequency of the sound you hear.

Explanation / Answer

In classical physics, where the speeds of source and the receiver relative to the medium are lower than the velocity of waves in the medium, the relationship between observed frequency f and emitted frequency fo is given by: f = [(V+Vr)/(V+Vs)] x fo Where V is the velocity of waves in the medium Vr is the velocity of the receiver relative to the medium; positive if the receiver is moving towards the source. Vs is the velocity of the source relative to the medium; positive if the source is moving away from the receiver. The frequency is decreased if either is moving away from the other. (a) By v = nLameda =>Lameda = 343/2517 = 0.136 m & n = 2517 Hz (b) f = [(V+Vr)/(V+Vs)] x fo =>f = [343/(343 - 28.9] x 2517 =>f = 2748.58 Hz (c) f = [(V+Vr)/(V+Vs)] x fo =>f = [(343+13.1)/(343 - 28.9)] x 2517 =>f = 2853.56 Hz

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.