RADIATION, LIGHT, AND ASTRONOMY
Instructor Copy
Part 1 – “The Machine”
a)
I have here a machine that tells us about some physical phenomena. I want the
class to determine how this machine works, and what the machine can tell us
about the world. In order to probe the machine, I propose that we put different
objects in front of, and around, “The Machine”. I want you to write down
observations while different tests occur – observe what works, and what doesn’t
work.
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Test the teddy bear, baseball glove, Lord of the Rings book
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Ask the class to offer suggestions of items to test
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Test my own hand, test a cold cup of water
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Ask the class to offer more suggestions of items to test
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Test a warm cup of water, cellphone, an iron
Ask the students to discuss their findings, and write them down on the worksheet.
b)
Objects with heat emit thermal radiation. We can think of radiation as energy
travelling out from a source into space. Somehow, this machine is detecting
radiation coming from hot objects. This is why a hot cup of water, and hands set
off the detector (body surface temperature is 32ºC).
Part 2 – Mmm, Smells like Physics!
Now that we know that objects with heat emit thermal radiation, we want to investigate
the nature of this radiation.
a)
Place the lightbulb across the room on a ladder – test to see if the microwave will
detect the light waves coming from the light.
b)
Place a radio across the room on the ladder – test to see if the microwave will
detect the radio waves coming from the radio.
c)
Place a microwave across the room on the ladder – test to see if the microwave
will detect the radio waves coming from the radio.
Ask the students to discuss their findings, and write them down on the worksheet.
“The Machine” is able to detect microwave radiation coming from a source. All around
us are electromagnetic waves, bouncing around the room, off the walls, floor. We can
think of ourselves as in a pool. Some of these EM waves, the light variety, we see with
our eyes. However, many of these waves travel right by us without our detection. Show
the electromagnetic spectrum, briefly talk about how the EM spectrum works.
Ask the students to think of examples of different types of light, and where they might fit
on the EM spectrum. Try to encourage on particular application – Astronomy.
Now place the light bulb close to the detector – test to see if there is a reading. And there
is! Explain why this is the case – objects with a certain temperature emit all types of
radiation – this is known as “Blackbody radiation”. This radiation comes from the
molecules inside of objects. When these molecules are moving around, they give off
radiation. However, how fast these molecules are moving determines the type of radiation
they give off.
Part 3 – The Machine, Revisited
Ask the students to guess how the machine works.
Explain that it is taking in EM waves which make electrons oscillate. These electrons
then generate a current – a current that is measured by the noise box. The box then gives
off a sound, depending on the current.
Part 4 – The Microwave Background
Our next task will be to generate a map of the microwave sky. In Astronomy, we turn our
telescopes to the sky, and scan back and forth in order to take images of distant sources.
That is exactly what I propose we do here – we will map a map of the microwave
radiation coming from that microwave on a ladder.
Explain how the mapping works.
Ask the students to draw what they think the map will look like.
Generate the map with the class.
Talk about space and stuff
Bonus – How does the Machine Work?