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Re: Rainbow applet



At 09:29 AM 9/25/99 -0500, Cliff Parker wrote:

If you look at the
"explanations" provided in high school textbooks you will see that
they aren't explanations at all. All they say is that light is
reflected and refracted within raindrops. Given such explanations a
student couldn't tell you whether red shows up on the outside or
the inside of a rainbow, and he wouldn't have a clue how to calculate
the angular size of the bow.

You have me here.
I must confess I do not fully understand the problem of the
rainbow and I tell my students so, because you can be sure
they will ask at some time during the year.

Check this out: It is a java applet that demonstrates the correct physics
of a rainbow.
http://www.phy.ntnu.edu.tw/java/Rainbow/rainbow.html

Note (!) that you can grab the incident ray with the mouse and drag it up
and down. Watch how the 1-bounce emergent ray (#3) moves one way, pauses
at the *caustic* angle, and then moves back. This is what produces the
primary bow at the caustic angle. Ditto for the 2-bounce emergent ray
(#4), which produces the secondary bow at a slightly different angle. Also
notice the little "3" and "4" markers sliding on the angle axis of the
intensity graph.


And BTW, on the page
http://alboot.ba.infn.it/www/didattica.html
there is a pointer not only to the rainbow applet, but scads of other
things. I haven't checked them all out, but if they are as cool as this
rainbow applet this is quite at trove.

______________________________________________________________
John S. Denker jsd@monmouth.com