Interference Colors

INTERLUDE: Hard and Soft Boundaries   Start the wave simulation at http://phet.colorado.edu/simulations/stringwave/stringWave.swf. Make the damping (friction) zero, and wiggle the string. Notice what happens when the wave reflects off the 'fixed end', and the 'loose end'. I like to call these hard boundary and soft boundary, respectively. Notice that the wave flips (crests become troughs) when reflecting off a hard boundary, and don't when they bounce off a soft boundary. This is important for understanding resonance.

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