Hologram Essay

Essay by BJ BrausenHigh School, 10th gradeF, February 1997

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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 the

real thing?

It all starts with light. Without it, you can't see. And

much like the ripples in a pond, light travels in waves. When

you look at, say, an apple, what you really see are the waves of

light reflected from it. Your two eyes each see a slightly

different view of the apple.

These different views tell you

about the apple's depth -its form and where it sits in relation

to other objects. Your brain processes this information so that

you see the apple, and the rest of the world, in 3-D. You can

look around objects, too -if the apple is blocking the view of

an orange behind it, you can just move your head to one side.

The apple seems to 'move' out of the way so you can see the

orange or even the back of the apple. If that seems a bit

obvious, just try looking behind something in a regular

photograph! You can't, because the photograph can't reproduce

the infinitely complicated waves of light reflected by objects;

the lens of a camera can only focus those waves into a flat, 2-D

image. But a hologram can capture...