試題詳解

42. An ambulance moves at a speed of 50 km/hr, and its siren emitting sound at a frequency of 5.0x10² Hz. What frequency of sound is heard by a runner who is running at 4 m/s approaching each other in the opposite direction (the speed of sound in air is 345 m/s)?
(A) 47 Hz
(B) 475 Hz
(C) 506 Hz
(D) 527 Hz
(E) 555 Hz