| MadSci Network: Physics |
Alexandra,
Admittedly, since I wasn't there for your experiment (and what you describe sounds like an *excellent* experiment) I can't answer your question with absolute certainty. However, I think I may have a likely explaination for the results you obtained...
The light we receive here on Earth has been scattered many times by the atmosphere. We receive the visible wavelengths of light thanks to atmospheric windows. Because our atmosphere is made up of many different types of particles, some wavelengths of light are absorbed more than others. As scientists, we generally state that there is a visible window of light which suggests that all visible wavelengths of light are transmitted through the atmosphere. This is true, but there's a catch...
Light from the sun does not emit at all wavelengths at equal strengths. Check out the light curve at the end of this web page. The sun emits the most light at visible wavelengths (~0.4-0.7 microns on the bottom axis of this plot), but at a decreasing rate. Now add in the additional complication of the atmosphere. Even though there is an atmospheric window at these wavelengths, some wavelengths are absorbed/scattered a bit more than others. From the curve, ozone appears to be the largest culprit at the visible wavelegths. I believe this may explain some of the discrepancies you saw.
Another more basic explaination would be the answer to the question, "Why is the sky blue?" Well, blue light is scattered by the atmosphere 4x more than red light, which is why the sky is blue, and which may explain why your temperature for blue was lower than that of red.
I hope that gets you going in the right direction,
Amber
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