http://www.rpi.edu/dept/phys/ScIT/InformationTransfer/reflrefr/rr_content/reflection_15.html
http://www.rpi.edu/dept/phys/ScIT/InformationTransfer/reflrefr/rr_content/reflection_15.html
 
 
http://www.kettering.edu/~drussell/Demos/reflect/reflect.html
http://www.kettering.edu/~drussell/Demos/reflect/reflect.html
 
 
 
A great set of animated gifs illustrating the operation of engines.