A student inquired today about pulses reflecting and possibly flipping over at,
say, the boundary between two strings.
When a pulse on a string reflects from a boundary with a more massive string,
the reflected wave is inverted. This follows from the displacement and slope
being continuous at the boundary. The flipping over requires a shorter
wavelength (and lower phase velocity) and longer k-vector in the second medium.
But I have no qualitative argument for this, without using equations.
Does anyone have a qualitative argument for this behavior, without the
equations: slower wave speed in the second medium (larger k, smaller
wavelength) causes the reflected wave to be flipped over?