일반물리학 1 — Waves-II: Problem 8

8 A sound source A and a reflecting surface B move directly toward each other. Relative to the air, the speed of source A is 20.0 m/s, the speed of surface B is 80.0 m/s, and the speed of sound is 329 m/s. The source emits waves at frequency 2000 Hz as measured in the source frame. In the reflector frame, what are the (a) frequency and (b) wavelength of the arriving sound waves? In the source frame, what are the (c) frequency and (d) wavelength of the sound waves reflected back to the source?