A very good web site to learn about laser is
How stuff works:
howstuffworks You will learn all you want
to know about lasers.
In our ScienceLine database we have an answer
to how CDs work. I have posted it here. Together
both should help you understand lasers and CDs.
How do CDs work? Electronics are often
times based in the "binary" language, meaning that
everything is presented by 0's and 1's. It
is the easiest scenario because you only need to
find out if something is "on" or "off." CD's are
composed of many concentric grooves, much like the
old vinyl records. Each groove of a CD is like a
long trench. However, the trench is not uniformly
deep, but rather there are two different
heights. Imagine the bottom of the trench
being a race track with a set of irregularly
spaced hurdles. Now, a laser shines into the
trench, hits the bottom, reflects back out, and
then hits a detector that records the event.
Depending on if the laser hits the bottom of
the trench or hits the top of a hurdle, a
different signal is observed by the detector.
Since we have only two levels, there are two
different output signals. One signal is assigned a
value of "0" and the other a value of "1" - this
is how binary information is stored on a disc! The
binary signal is then decoded by the CD player to
be turned into the music that you hear.
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