A train sounds its whistle at a constant frequency as it passes by the platform. Compared to the sound emitted by the whistle, the sound that people on the platform hear as the train moves away has a frequency that is ... -higher
-the same
-lower
-exactly half

Which statement best describes the superposition principle? a.) if two in-phase waves arrive simultaneously at a point, their amplitudes add up b.) if two out-of-phase waves arrive simultaneously at a point, their amplitudes add up c.) if two in-phase waves arrive at a point one after another, their amplitudes add up d.) if two out-of-phase waves arrive at a point one after another, their amplitudes adds up