A wave yi = 0.3 cos (40t − 0.2x) is travelling along a string toward a boundary at x = 0. What are the expressions for the reflected waves if the string has a fixed end and at x = 0. Assume SI units.
If the end is fixed then the wave reflects back with a phase change of π. So the wave equation will be y = 0.3 cos (0.2x + 40t + π)
Since the wave moves in opposite direction. The sign changes to +.