🚀 go-pugleaf

In article <1992Jul20.224509.15546@fs7.ece.cmu.edu> snyder@henry.ece.cmu.edu (John Snyder) writes:
>
>So, in simple form, what is the correct explanation (including the double
>and triple rainbows)?
>
>John
>snyder@henry.ece.cmu.edu
>
>
>
	Hard to explain without graphics.. Light enters the raindrop. The
raindrop is a sphere.  At the point where the light enters the raindrop from
the air, some of the light is reflected.  The reflected light has a phase
change.  The light which continues into the raindrop leaves the raindrop
into the air. At THAT point, some light is reflected. There is no phase
change.
	(I could've gotten my phase changes mixed up.)

	NOW. You have two rays of light leaving the raindrop in the same
direction-- one with a phase change of 1/2 lamda (wavelength) and the other
with a phase change of 2nd (because the travels further-- NOT REALLY a phase
change, but let's call it that..) (n is the refraction coeffiction for the
water, and d is the distance through the drop that the ray traveled before
being reflected.)
	So there is an intereference pattern, and a few wavelengths produce
maxima i.e. they are the brightest ones. Usually only one of these
wavelengths are visible.  Then you sum up all the rays going into the drop.
THe spherical nature of the drop accounts for differing 'd' values, and thus
light that enters the raindrop at different places have different maxima
colors.  THe spherical nature of the raindrop also refracts the light into
the arch.
	I am GUESSING that the second and third arches are due to more than
one visible maximum? That's a guess.
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