First, consider case A: An observer flies in a plane toward a stationary 600 Hz siren at 1/4 the speed of sound. Now consider case B: a plane carries a 600 Hz siren at 1/4 the speed of sound towards the observer in the airport tower. What is different about these two situations that can justify why the Doppler shifts are not equal? Group of answer choices The rate at which the magnitude of their displacements changes is the same. The rate at which the magnitude of their displacements changes is not the same. In one case, the source moving through the medium actually shortens the sound's wavelengthsa different effect on the observed frequency than when an observer moving through the medium simply increases the rate at which (un-shortened) wavefronts are encountered. Wind would be a bigger factor in the case of the siren on the plane. The sound of the engine would cause interference when the observer is on the plane