Physics of light and temperature

Published by in science on January 27th, 2008

Does anyone understand the physics of why the air temperature measured when different wavelengths of light cast by a refracting prism vary? My son investigated this for his science fair project this year (4th grade) and I honestly don’t understand the reasons why this happens. If you have ideas on this, please leave a comment here, on the post he left over on Learning Signs, or on the VoiceThread he created explaining his project and his conclusions. :-)

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2 Comments »
  • http://school20.siglersite.com James Sigler

    An excellent scientific experiment!

    I suspect that your unexpected results were because of an hidden variable. I think the results can be explained partly by the greenhouse effect.

    Ultraviolet light can pass through the window, but the infrared (heat) couldn’t. When the sunlight passed through the glass window the infrared was trapped outside the window and the ultraviolet light changed to infrared light. Since the visible red light passed through the window better than the infrared, I think that is why the red was warmer than the infrared. There was more red light hitting the thermometer than infrared light.

    Can you try the experiment again without the window? Would you get the same results?

  • http://www.wesfryer.com Wesley Fryer

    James: Thanks so much for sharing these ideas! I’ll tell Alexander in the morning and suggest he redoes the experiment without the window– it will be a little chilly to have the door open but it can be done, certainly! Excellent! We’ll report our new results!

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