This simulation shows a wave-pulse on a string propagating and hitting the end of the string. If you choose the end of the string to be fixed, you will see one form of reflection. If you choose the end of the string to be free to move in the vertical direction, you will see something subtly different. Look carefully at what is happening, what this means in terms of phase shifts, and what the resultant disturbance is in each case. The total disturbance at any place is the sum of the contributions of the forward going and reflected pulses.
Pressing Run will start the simulation. You may pause the simulation or step your way through it, if you find the free running one too fast to follow. Credits