120 lines
7.4 KiB
Plaintext
120 lines
7.4 KiB
Plaintext
ÜÜÜÜÜÜÜÜÜÜÜÜÜ ÜÜÜ ÜÜÜÜ
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ÜÛÛÛÛÛÛÛÛßÛßßßßßÛÛÜ ÜÜßßßßÜÜÜÜ ÜÛÜ ÜÛÛÛÛÛÛÛÛÜÜÜÜÜÛßß ßÛÛ
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ßÛÛÛÛÛÛÛÛÛÛÛÛÛÛÜ ßÛÛ ÜÛÛÛÜÛÛÜÜÜ ßÛÛÛÛÜ ßÛÛÛÛÛÛÛÜÛÛÜÜÜÛÛÝ Ûß
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ßßßÛÛÛÛÛÛÛÛÛÛÜ ÞÝ ÛÛÛÛÛÛÛÛÛÛÛßßÛÜÞÛÛÛ ÛÛÛÛÛÜ ßßÛÛÛÞß
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Mo.iMP ÜÛÛÜ ßÛÛÛÛÛÛÛÝÛ ÞÛÛÛÛÛÛÛÛÛ ÞÛÛÛÛ ÞÛÛÛÛÛÝ ßÛß
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ÜÛÛÛÛÛÛÛ ÛÛÛÛÛÛÛÛÝ ÞÛÛÛÛÛÛÛÛÝ ÛÛÛ ÛÛÛÛÛÛ
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ÜÛÛÛÛÛÛÛÝ ÞÛÛÛÛÛÛÛÛ ÞÛÛÛÛÛÛÛÛ ß ÞÛÛÛÛÛÛÜ ÜÛ
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ÜÛÛÛÛÛÛÛÝ ÛÛÛÛÛÛÛÛ ÛÛÛÛÛÛÛÛÝ ÞÞÛÛÛÛÛÛÛÛÛß
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ÜÛßÛÛÛÛÛÛ ÜÜ ÛÛÛÛÛÛÛÛÝ ÛÛÞÛÛÛÛÛÝ ÞÛÛÛÛÛÛßß
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ÜÛßÛÛÛÛÛÛÜÛÛÛÛÜÞÛÛÛÛÛÛÛÛ ÞÛ ßÛÛÛÛÛ Ü ÛÝÛÛÛÛÛ Ü
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ÜÛ ÞÛÛÛÛÛÛÛÛÛÛß ÛÛÛÛÛÛÛÛÛ ßÛÜ ßÛÛÛÜÜ ÜÜÛÛÛß ÞÛ ÞÛÛÛÝ ÜÜÛÛ
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ÛÛ ÛÛÛÛÛÛÛÛß ÛÛÛÛÛÛÛÛÛÛÜ ßÛÜ ßßÛÛÛÛÛÛÛÛÛß ÜÜÜß ÛÛÛÛÜÜÜÜÜÜÜÛÛÛÛÛß
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ßÛÜ ÜÛÛÛß ßÛÛÛÛÛÛÛÛÛÛÜ ßßÜÜ ßßÜÛÛßß ßÛÛÜ ßßßÛßÛÛÛÛÛÛÛßß
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ßßßßß ßßÛÛß ßßßßß ßßßßßßßßßßßßß
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ARRoGANT CoURiERS WiTH ESSaYS
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Grade Level: Type of Work Subject/Topic is on:
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[ ]6-8 [ ]Class Notes [Essay on Holograms ]
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[x]9-10 [ ]Cliff Notes [ ]
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[ ]11-12 [ ]Essay/Report [ ]
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[ ]College [ ]Misc [ ]
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Dizzed: 11/94 # of Words:1051 School: ? State: ?
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ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>Chop Here>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ
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Toss a pebble in a pondsee the ripples? Now drop two pebbles close
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together. Look at what happens when the two sets of waves combine you get
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a new wave! When a crest and a trough meet, they cancel out and the water
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goes flat. When two crests meet, they produce one, bigger crest. When two
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troughs collide, they make a single, deeper trough. Believe it or not,
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you've just found a key to understanding how a hologram works. But what do
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waves in a pond have to do with those amazing three dimensional pictures?
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How do waves make a hologram look like the real thing?
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It all starts with light. Without it, you can't see. And much like the
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ripples in a pond, light travels in waves. When you look at, say, an
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apple, what you really see are the waves of light reflected from it. Your
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two eyes each see a slightly different view of the apple. These different
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views tell you about the apple's depthits form and where it sits in
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relation to other objects. Your brain processes this information so that
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you see the apple, and the rest of the world, in 3-D. You can look around
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objects, tooif the apple is blocking the view of an orange behind it, you
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can just move your head to one side. The apple seems to "move" out of the
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way so you can see the orange or even the back of the apple. If that
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seems a bit obvious, just try looking behind something in a regular
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photograph! You can't, because the photograph can't reproduce the
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infinitely complicated waves of light reflected by objects; the lens of a
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camera can only focus those waves into a flat, 2-D image. But a hologram
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can capture a 3-D image so lifelike that you can look around the image of
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the apple to an orange in the backgroundand it's all thanks to the special
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kind of light waves produced by a laser.
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"Normal" white light from the sun or a lightbulb is a combination of
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every colour of light in the spectruma mush of different waves that's
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useless for holograms. But a laser shines light in a thin, intense beam
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that's just one colour. That means laser light waves are uniform and in
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step. When two laser beams intersect, like two sets of ripples meeting in
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a pond, they produce a single new wave pattern: the hologram. Here's how
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it happens: Light coming from a laser is split into two beams, called the
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object beam and the reference beam. Spread by lenses and bounced off a
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mirror, the object beam hits the apple. Light waves reflect from the apple
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towards a photographic film. The reference beam heads straight to the film
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without hitting the apple. The two sets of waves meet and create a new
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wave pattern that hits the film and exposes it. On the film all you can
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see is a mass of dark and light swirls it doesn't look like an apple at
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all! But shine the laser reference beam through the film once more and the
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pattern of swirls bends the light to re create the original reflection
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waves from the appleexactly.
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Not all holograms work this waysome use plastics instead of photographic
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film, others are visible in normal light. But all holograms are created
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with lasersand new waves.
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All Thought Up and No Place to Go
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Holograms were invented in 1947 by Hungarian scientist Dennis Gabor, but
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they were ignored for years. Why? Like many great ideas, Gabor's theory
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about light waves was ahead of its time. The lasers needed to produce
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clean wavesand thus clean 3-D imagesweren't invented until 1960. Gabor
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coined the name for his photographic technique from holos and gramma, Greek
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for "the whole message. " But for more than a decade, Gabor had only half
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the words. Gabor's contribution to science was recognized at last in 1971
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with a Nobel Prize. He's got a chance for a last laugh, too. A perfect
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holographic portrait of the late scientist looking up from his desk with a
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smile could go on fooling viewers into saying hello forever. Actor
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Laurence Olivier has also achieved that kind of immortality a hologram of
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the 80 year-old can be seen these days on the stage in London, in a
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musical called Time.
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New Waves
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When it comes to looking at the future uses of holography, pictures are
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anything but the whole picture. Here are just a couple of the more
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unusual possibilities. Consider this: you're in a windowless room in the
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middle of an office tower, but you're reading by the light of the noonday
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sun! How can this be? A new invention that incorporates holograms into
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widow glazings makes it possible. Holograms can bend light to create
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complex 3 D images, but they can also simply redirect light rays. The
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window glaze holograms could focus sunlight coming through a window into a
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narrow beam, funnel it into an air duct with reflective walls above the
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ceiling and send it down the hall to your windowless cubbyhole. That could
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cut lighting costs and conserve energy. The holograms could even guide
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sunlight into the gloomy gaps between city skyscrapers and since they can
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bend light of different colors in different directions, they could be used
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to filter out the hot infrared light rays that stream through your car
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windows to bake you on summer days.
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Or, how about holding an entire library in the palm of your hand?
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Holography makes it theoretically possible. Words or pictures could be
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translated into a code of alternating light and dark spots and stored in an
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unbelievably tiny space. That's because light waves are very, very
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skinny. You could lay about 1000 lightwaves side by side across the width
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of the period at the end of this sentence. One calculation holds that by
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using holograms, the U. S. Library of Congress could be stored in the
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space of a sugar cube. For now, holographic data storage remains little
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more than a fascinating idea because the materials needed to do the job
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haven't been invented yet. But it's clear that holograms, which author
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Isaac Asimov called "the greatest advance in imaging since the eye" will
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continue to make waves in the world of science.
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