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Unit 12: Alternative Energy Page 24 of 31
When sunlight is concentrated by heated to extremely high
passing it through a lens, the result temperatures.
can be an intensely bright and not Concentrated sunlight also has
spot of light. Even a small been used to purify polluted
magnifying glass can increase the ground water. The ultraviolet
intensity of the sun enough to set radiation in sunlight can break
wood and paper on fire. We are down organic pollutants into
using a light bulb rather than carbon dioxide, water, and
sunlight for this experiment harmless chlorine ions. This
because concentrated sunlight Can procedure has been successfully
be very harmful to your eyes. carried out at the Lawrence
NEVER LOOK AT A CONCENTRATED Livermore Laboratory in California.
IMAGE OF THE SUN. In the laboratory, up to 100,000
The United States Department of gallons of contaminated water
Energy's National Renewable could be treated in one day.
Energy Laboratory in Colorado uses
solar energy to operate a special
furnace. This high-temperature Other Things to Try
solar furnace uses a lens to Trace the exact size and shape of
concentrate sunlight. A heliostat (a the magnifying lens on a piece of
device used to track the motion of paper. Cut out this piece of paper
the sun across the sky) is used so and tape in on the wall. Focus the
that the image reflected from a image of the lamp on this piece of
mirror is always directed at the paper and copy the bulb image on
same spot. The lens is used to the paper. Compare the size of the
concentrate sunlight from a mirror bulb image to the size of the piece
to an area about the size of a of paper. How much bigger is the
penny. This concentrated sunlight lens than the focused image of the
has the energy of 20,000 suns bulb? Use this ratio of sizes to
shining in one spot. estimate the increase in the
In less than half a second, the brightness of the image.
temperature can be raised to Can you explain why the image of
1,720° C (3,128° F) which is hot the bulb is upside down when it is
enough to melt sand. This high- projected on the wall? See if you
temperature solar furnace is being can find information about optics in
used to harden steel and to make a book or encyclopedia that could
ceramic materials that must be
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