Physics
Physics
Problem
A 520 Hz tuning fork is struck and held next to a stationary listener on the side of a road. A car with a horn that has a rest frequency of 500 Hz passes by at 30 m/s. The speed of sound is 340 m/s. What beat frequency will the listener hear immediately after the car has passed? a) b) c) d)Intuitive explanation
The key is recognizing that beats occur when two sound waves of slightly different frequencies interfere. After the car passes, it's moving away from the stationary listener, so the Doppler effect shifts the horn's frequency downward. You'll need to calculate the observed frequency of the receding horn using the Doppler formula, then find the frequency difference between it and the tuning fork—that difference is your beat frequency.
Intuitive explanation
The key is recognizing that beats occur when two sound waves of slightly different frequencies interfere. After the car passes, it's moving away from the stationary listener, so the Doppler effect shifts the horn's frequency downward. You'll need to calculate the observed frequency of the receding horn using the Doppler formula, then find the frequency difference between it and the tuning fork—that difference is your beat frequency.