Holograms
Toss a pebble in a pond -see the ripples? Now drop two
pebbles close together. Look at what happens when the two sets
of waves combine -you get a new wave! When a crest and a trough
meet, they cancel out and the water goes flat. When two crests
meet, they produce one, bigger crest. When two troughs collide,
they make a single, deeper trough. Believe it or not, you've
just found a key to understanding how a hologram works. But what
do waves in a pond have to do with those amazing three-
dimensional pictures? How do waves make a hologram look like t…
