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Now
that you have their attention, you are ready to introduce a field
of technology called
“optical engineering”.
- Hold
up the silicon wafer (shiny side out) and the large
silica lens. Ask if anyone can identify them. [The
lens is usually easy. The students will likely refer to the wafer
as a mirror.]
- Identify
the wafer as single crystal silicon, a pure elemental substance
and the basis for all computers (the chips and microcircuits).
Show them the reverse side of the wafer which is dull, and explain
that this side is ground and the other is polished to a mirror
surface. Some optical engineers develop the technologies for turning
rough silicon wafers into integrated circuits for making computer
chips. [You may want to elaborate on this.]
- Hand
out copies of the periodic table of elements (useful for 8-9th
grade and higher) and help the students locate silicon (#14) and
oxygen (#8).
- State
that the periodic table is a visual means for displaying all of
the elements known to man - every bit of matter in the universe
is composed of one or more of these elements. Ceramic engineers,
chemists, materials scientists, geologists, and optical engineers
work with many of these elements and the compounds they form.
- Explain
that the only difference between the silicon wafer and the silica
lens is oxygen. Point out how a little oxygen turns a visibly
opaque material into a visibly clear one. Suggest that if we were
aliens whose vision was in the infrared, the silica lens would
look opaque and the silicon wafer would look transparent! Mention
that optical engineers build lenses into systems that image light,
such as the Hubble Space Telescope, the Chandra X-Ray Telescope,
or the new digital cameras that record images on silicon.
Copyright
by Stephen D. Jacobs, Rebecca L. Coppens and Christine Andrews-Angelo
December 24, 2001
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