Date: Tue, 12 Feb 2002 19:11:27 -0500

Author: Sue and Tom Gill

Subject: Re: heat transfer


Some IR/heat radiation demo ideas

With the radiometer - Place a bunsen burner near it and when it's adjusted
properly (nice blue flame) the radiometer will hardly budge. Adjust it so
the flame is very orange and it turns.

If you have a parabolic reflector, you can aim a beam of light from a
powerful incandescent bulb onto a student's face (with proper warning of
course). They will feel the warmth nearly instantly and you can turn it on
and off by blocking the beam and they will feel the hot/cool nearly
instantaneously as well.

If you have a large lens or mirror, try converging sunlight on paper.
Especially noteworthy would be the difference in how easily you can catch a
black vs. white sheet of paper on fire. I use a Fresnel lens from a
scrapped overhead for this.

Something I've never been happy with the results of - use a diffraction
grating to get a spectrum from the sun or other intense source and try to
measure a temperature increase next to the red portion where the IR should
be. Also, Radio Shack sells small credit card sized IR detectors that must
be "charged" in light (esp. UV) and can then visibly show the IR from a
remote control. I wonder if they would also show the IR from the
diffraction grating?

Take apart an old film projector - chances are you'll find a blue-colored
filter in it that helps block the IR thus keeping the film cooler but not
making it too much dimmer. If you run the projector first, it will be hot
when you remove it (because it was absorbing IR). You can use the filter to
demonstrate that remote controls are IR based by showing that they won't
work when beamed through the filter.

Hope something here is useful!

Tom Gill
Central Columbia HS
Bloomsburg, PA

----- Original Message -----
From: "Anthony Lapinski"
Sent: Tuesday, February 12, 2002 9:34 AM
Subject: heat transfer

> I'm teaching a unit on heat to my regular physics class. Next topic is
> electricity. I need to talk about conduction, convection, and radiation.
> What is the best way to explain radiation without mentioning EM waves
> (something they might not understand). Conduction and convection are
> simple, but they have a hard time with radiation.
> Radiation demos?
> sunlight
> radiometer
> anything else?
> Thanks, tappers!