Thanks, Mark! All very valuable information that I'm saving to correct my
kewords!
Tina
On Tue, Jun 24, 2014 at 2:07 PM, Mark Marr-Lyon <mark.marrlyon@xxxxxxxxx>
wrote:
> As long as this list has grammar and punctuation pedants, we might as well
> have an atmospheric optics one as well :)
>
> Moose's photo is an example of cloud iridescence, which is caused by
> diffraction (not refraction) of light by small cloud droplets or crystals.
>
> Halos are caused by refraction through hexagonal ice crystals. There are
> many different kinds of halos and complex displays can be quite
> spectacular. One of the more common ones is the 22 degree halo, and sundogs
> are bright spots in this halo caused by alignment of the crystals.
>
> The rainbow is pretty straightforward refraction and reflection, with the
> primary bow caused by one bounce off the back of the droplet and the
> secondary bow caused by two bounces. Supernumerary bows, one of which is
> visible in John's photo inside of the purple band, are interference effects
> and can't be described with geometric optics.
>
> The glory in Tina's photos is also more complicated and can't be described
> by geometric optics alone either. It's also harder to see since the
> observer has to be above the clouds, as Tina was in Machu Picchu.
>
> A corona is another diffraction phenomena, and is an Airy disk seen around
> the light source, like the sun or moon.
>
> There's lots of good web sites on atmospheric optics around for anyone who
> is interested.
>
> Mark
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>
>
--
Tina Manley
http:// <http://tina-manley.artistwebsites.com/>www.tinamanley.com
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