Date: Mon Nov 9 16:29:35 2009

Author: William Beaty

Subject: Re: Lightning affects rainbows?!


On Mon, 9 Nov 2009, Richard Berg wrote:

> It looks to me like the whole thing changes its "look" at some time. When
> you have a lightning strike and the concomitant high pressure heat pulse
> leaving the region it can result in adiabatic cooling when the pulse expands.

I bet it's electromagnetic though. Or optical. If the region is a few
hundred feet across (or a few thousand,) then it should be easy to see an
acoustic wave sweep across the bright mist. I don't see one, but maybe
I'm not looking closely. The whole region seems to alter as one,
suggesting EM rather than thunder as the driver.

> This would cause additional condensation of water vapor in the region and
> lead to the effect that we see. This is what you see in an atomic bomb
> explosion such as this one:
> Rapid expansion of the air in the region of the explosion leads to adiabatic
> cooling, forming lots of small water droplets which we view as a white cloud.
> Dick
> ***********************************************************************
> Dr. Richard E. Berg, Professor of the Practice
> Physics Lecture-Demonstration Facility
> U.S. mail address:
> Department of Physics
> University of Maryland
> College Park, MD 20742-4111
> Phone: (301) 405-5994
> FAX: (301) 314-9525
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