ClipArt ETC
"Start a trough from A. At the moment of its reflection as a crest a B, start a crest at A as shown. The two crests will meet near the middle of the rope. The crest at the point and moment of meeting results from two forces acting in the same direction; their resultatnt is greater than either of the components." -Avery 1895

Constructive Interference

"Start a trough from A. At the moment of its reflection as a crest a B, start a crest at A as shown.…

"Using the rope...start a crest at A. At the moment of its reflection at B as a trough, start a second crest at A. The trough and crest will meet near the middle of the rope. the rope particles at this point, being thus simultaneously acted upon by opposite forces, will remain at rest or nearly so." -Avery 1895

Destructive Interference

"Using the rope...start a crest at A. At the moment of its reflection at B as a trough, start a second…