Sources of “Light,” Detectors
and Shields
Making the invisible visible
Kevin McReynolds
(adopted from “Invisible Universe,” Lawrence Hall
of Science, UC at Berkeley, Stephen Pompea,
Alan Gould, Lincoln Bergman, 2002.)
www.lhsgems.org
This workshop funded by NASA Office of Education
Grant NNX09AH83A and supported by the Georgia
Department of Education, Columbus State University,
and Georgia Southern University
First…
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contact
• I’ll send you the presentation and lab
documentation electronically.
• A little about me…
• This presentation is sponsored by GEARS
– Georgians Experience Astronomy Research in Schools
• Please fill out the presentation evaluation
at the end
GEARS:
Georgians Experience Astronomy Research in Schools
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Chem., Physics, Phys. Sci., GPS
High School Teachers Only This Year
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This workshop funded by NASA Office of Education Grant
NNX09AH83A and supported by the Georgia Department of
Education, Columbus State University, and Georgia Southern
University
Background
• We are surrounded by electromagnetic
radiation.
• Most of it is invisible
• Much of it is detectible
• Electromagnetic spectrum review…
– Powers of ten,
– Making a visual model
– Wavelength = (speed of light) / frequency
• Check out http://chandra.harvard.edu/ for great
ideas and resources under the “Education” tab.
Powers of Ten
Order these from smallest to largest
10-3
102
100
10-1
105
101
10-5
103
10-2
104
10-4
106
EMR spectrum
from http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
Why this is important
•
From http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html
Activity overview
• Predict the shielding ability of various
common materials.
• Rotate through lab stations to test
predictions.
• Each lab station has an EMR emitter and
various materials (possible shields).
» Some stations will have safety concerns…
Shielding materials
•
•
•
•
•
•
•
•
Metal screens
Plastic screens
Wax paper
Aluminum foil
Plastic bags
Cloth remnants (cotton, silk)
Overheat transparency sheet
White paper
Station 1
• Visible light
• Emitter = mag-lite flashlight
• Detector = plain, white paper & the eye
Station 2
• Infrared (far)
• Emitter = heat lamp bulb
• Detector = your hand
» Safety note: DO NOT get materials too close to the
bulb. Protect your hand from extended exposure
Station 3
• Infrared (near)
• Emitter = TV/VCR/DVD remote
• Detector = digital camera / camera phone
» Note: you may be able to connect the output of the
camera to a TV to demonstrate to the whole class
what should be seen
Station 4
• Radio waves (FM)
• Emitter = FM radio tuned to a clear station
• Detector = your ear
» Note: Be sure to cover the radio completely. Battery
operated radios work better because the cord of
plug-in types acts as an antenna
Station 5
• Radio waves (AM)
• Emitter: Radio tuned to a
clear AM station
• Detector: your ear
» Note: Be sure to cover the
radio completely. Battery
operated radios work better
because the cord of plug-in
types acts as an antenna
Station 6
• Ultraviolet light
• Emitter = black light bulb
• Detector = UV beads (look for color
change)
» Safety note: long term exposure to the eye is NOT
recommended. DO NOT use “short” UV sources
intended to sterilize surfaces.
» Note: for best results work in the darkest part of the
room. Use just a few beads at a time. Have a
“recovery” location for exposed beads.
» Tonic water, TIDE detergent &/or packing peanuts
also work well.
Let’s investigate
• Take about 25 minutes
• Form groups around the room at each
station
• Rotate through each station
– Choose materials to test at each station
– Record results as you go.
Going Further:
ways to differentiate
• Research the “whys” of the observed
behaviors
• Investigate is distance affects the
outcomes
• Does reflection affect outcomes?
• Other ideas?
Teacher notes
• This requires a great deal of materials’
prep.
• Store all materials together in large ziptype plastic bags
– Quick access
– Reduce subsequent set-up time
• It’s worth it!
Workshop Reflections
• What written questions could use to
accompany this activity?
• How are the terms transparent,
translucent, opaque related to this activity?
• What aspects of the EMR did we not test?
• What is wrong with Superman’s X-ray
vision?