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News Release 06-127 - Video

Lesson in Light

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David Snider describes the light-polarizing filter lesson from his course.
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University of South Florida engineering professor David Snider uses light-polarizing filters to explain fundamental properties of electromagnetic radiation to his students.

Credit: University of South Florida

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Video Transcript:

We went outdoors and we looked at a section of the sky in which sunlight comes bouncing off of the air molecules  the blue light  and it's un-polarized. And to illustrate the principles of the polarizing filter, we hold the polarizing filter up which just passes about half of the light which is un-polarized. And then we take a second polarization filter and if it's aligned with the first one, nothing happens; but if you turn it 90 degrees, then none of the light that the first filter polarizes gets through the second filter and so it turns black altogether. And so I had the students take away and just use one polarizing filter and see if they could find certain sky directions where they could completely blacken out the sky. And these actually happen when you're observing at 90 degrees to the sun. We tried to show this as well with the camera pointing at that direction and using a single filter.

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