8.03 at ESG - Notes

Reflected Pulses

Start by taking a look at Long Pulse, Reflected. The wave is incident on a fixed end at x = 0 from the -x-direction, and it sure looks like an incoming wave that is reflected without inversion.
(For display purposes, the animation is looped; the wave is not intended to be periodic. To avoid long loading time, only 100 frames were used, so the animation may not be really smooth.)

This is a contrived example. The wave used as the incident wave (a hyperbolic tangent, appropriately displaced and normalized) has infinite extent. The inverted reflected wave exactly cancels the incident wave, leaving a finite region where the sum of the incident and reflected waves is zero.

So, take a look at Long Pulse, Reflected, with Incident and Reflected Waves.
In this animation, the incident wave (green) and the reflected wave (cyan) are shown for x > 0, as well as x < 0, along with their sum (magenta).
(The incident and reflected waves are shown displaced vertically for display purposes.)

So, what's really going on here? Some of us think we know, but you make the call.

Back to the Pulses on a Struck String page.