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Re: Dry "wet" roads



A ten year old might accept that sometimes the light rays that
make images in our eyes are bent as though by a mirror,
or a wet surface.
She might accept that the effective speed of light varies,
traveling slowly in water, faster in cold air, faster yet in hot air,
and fastest in no air. Where there is a speed gradient of this kind,
say the layer of hot air close to the blacktop road,
the variation bends the beam, the side traveling fastest turning in
upon the rest. There is something of the same kind going on when
radio waves which might be lost in space, are bent back to land
again at distant radio receivers well over the horizon,
one could propose.

Brian

At 05:58 AM 4/18/2003 -0400, you wrote:
A class of fourth and fifth grade students have emailed me some questions
about light. They are all good questions and a challenge to answer in the
vocabulary of this age group. However, one has me a bit stumped. Can anyone
point me in a good direction for answering the following?
Why does a road appear wet on a hot day?
We are having rainy weather here now, but I am assuming they are asking
about what we see at low angles from the road surface.

Thanks.

Richard
-----------------------------
Dr. Richard L. Bowman
Professor of Physics / Dir. of Academic Computing
Bridgewater College
Bridgewater, VA 22812
http://www.bridgewater.edu/~rbowman/