PHYSICS · Subjective · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
A long string is fixed at x=0. One end of the string can be moved back and forth to generate a wave of frequency 120Hz that travels with speed 48m s−1 towards the fixed end. The fixed point begins to move slowly away from the generator with a constant speed of 2.0m s−1 along the +x-direction just as the first few wave-fronts arrive.
(a) Determine the frequency of the wave as received by the receding point at x=0 just before reflection.
(b) Assuming perfect reflection at that receding point, find the frequency of the reflected wave as sensed by a student standing at the generator.
(c) If the student simultaneously hears the original 120Hz tone from the generator and the reflected tone from the moving point, calculate the beat frequency observed.