Sunday, October 30, 2011

Quadruple rainbow observed and shot

I am late to this post, but within the calendar month of the news. I'm slow! But many of these items I post so I can easily find them later.

In any event, here's the fairly undramatic photo:

MSNBC's story at the end of this link explains why the photo doesn't knock your socks off. The BBC's take is here.

One thing to notice, the camera is aimed sunward.

I give a fairly robust lesson in the physics and geometry of rainbows. You should be able to find the materials at these links:
1. "Understanding Rainbows" Springboard (student worksheet)
2. "Understanding Rainbows" Springboard (answers)
3. "Understanding Rainbows" Presentation (interactive QuickTime)

Among the things we learn: the primary rainbow shows up at about 40°-42° around the anti-solar direction, and the secondary is out at 51°-53°. We look away from the sun to see such rainbows.

The geometry of the tertiary rainbow places it 38°-43° from the solar direction. The quaternary rainbow is similarly sunward.

Images of the tertiary and quaternary rainbows are reminiscent of the discovery of the outermost planets. Photographers aim their cameras to where the faint rainbows should be, Without seeing the rainbows with their own eyes, they shoot the images nonetheless. They then post-process the hell out of the images, beefing up contrast and saturation. And voila! Third/fourth order rainbows are revealed.

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