Calculating Frequency of Sound Waves from Moving Bus
Explanation:
When bus is approaching the stand where the student is standing:
The frequency emitted by the horn is 440 Hz. The speed of sound is 330 m/s and the bus is traveling at 20.0 m/s.
The formula to calculate the frequency heard by the student when the bus is approaching is:
f1 = f0 * v / (v - vb)
Plugging in the values:
f1 = 440 * (330) / (330 - 20)
f1 = 468 Hz
When the bus is at the crossing:
The frequency heard by the student remains the same as the emitted frequency, which is 440 Hz.
When the bus is receding from the stand:
The formula to calculate the frequency heard by the student when the bus is receding is:
f2 = f0 * v / (v + vb)
Plugging in the values:
f2 = 440 * (330) / (330 + 20)
f2 = 415 Hz
Therefore, the correct answer is A. The student will hear 468 Hz while the bus is approaching, 440 Hz at the crossing, and 415 Hz while the bus is receding.