Ripple Tank applet revisited.

http://www.falstad.com/ripple/

Choose "2 sources" or "Double slit" to review the phenomena discussed in class.

Holography

Diffraction and Holography

When light passes through small openings or around barriers, it can actually interfere with itself - this is called diffraction. Like interference, patterns can result - and these patterns are related to the opening or barrier that caused the diffraction.

Holography is an interference phenomenon, caused by two beams - a reference beam, coming from the laser, and an object beam (which reflected off the object). This interference pattern is burned into the film emulsion of holographic film. It can be reconstructed when light passes through it again.

Interference and Diffraction

Consider 2 waves meeting each other in the same space. Their energies (AKA wave amplitudes) can add (or subtract). This phenomenon is called interference. If you've ever added sine waves on a calculator before, the effect is similar - and sometimes also called superposition.

Crests can add to other crests or cancel with troughs - however, it's usually some combination, depending on the waves in question. And often, beautiful "interference patterns" can result.

Camera and Eye