Reflections at Boundaries

So how do we get two waves in the same medium?

When a wave is confined to a medium (such as on a string), when it reaches a boundary it will reflect.

At a fixed end the displacement wave is inverted.

Reflection from a fixed boundary:

Figure: Damped Vibration, animation courtesy of Dr. Dan Russell, Penn State University.

At a free end the displacement wave is not inverted.

Reflection from a free boundary:

Figure: Damped Vibration, animation courtesy of Dr. Dan Russell, Penn State University.