and other animal defense strategies
escape
camouflage
playing dead (possums, snakes)
trickery, mimicry
physical : quills, shell
chemical (skunks, stinkbugs, bobardier beetles...)
some unusual defenses
...some more
Links:
February 2020
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I always stert with a bit of history:
Way back, the fastest way to send messages was by carrying them by a courier
on horseback.
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In the late 1700's in France...
High-speed communication
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Telegraph Samuel Morse 1838
Morse code generator
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Telegraph Samuel Morse 1838
Via radio waves: 1890's James Clark Maxwell, Heinrich Hertz,
Nicola Tesla, Guglielmo Marconi
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Alexander Graham Bell patents the telephone 1876
1915 coast-to-coast call
digital data over the phone line
Telephone modem
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Radio & wire: frequency, wavelength, line-of-sight, analog/digital
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analog-to-digital
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To show how this works, I used a prism and a laser pointer to show the transition between
refraction and tota internal reflection as you change the angle of the beam.
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Total internal reflection is of course how optical fibers work. I have some broken fibers.
Removing protective layers, you can see the glass fiber itself, which is about the thickness
of a human hair.
I also have some 1-mm plastic wavelength-shifting fibers. They are bigger than the glass optical
fibers, and they also light up along the length. In addition, they light up green even if you
use the purple laser. But that's a whole nother story.
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Bring:
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- Fixture + bucket
- Laser pointers (with spare batteries)
- Towel
- Funnel
- Optical fibers
- Wavelength-shifting fibers
- 3L bottle with water
- Container with a little bit of milk
- Clear rectangular container
- Prism (in cardboard holder)
- Tape
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The fixture
Why make a fixture? I have one hour in the classroom, and no advance setup time. I have a
small table to work on. This fixture holds all the bits firmly in place, and everything
is easily adjustable, so no time is lost. The base plate has a holder for the bottle, rolled
from cardboard.
A block with notches for rubber bands is attached. The clothespin functions as the switch
for the laser. Note I glued a piece of a straw into the bottle, instead of just making a hole.
This ensures that the stream of water is (initially) very smooth. The cardboard box that holds
everything serves as a raised platform. Since everything gets wet, the fixture gets a coat of
paint, and I put some plastic shelf paper on the box.
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Links::
March 2022
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