Sunday, August 3, 2014

Natural Lenses

When I was about 12 years old,
I visited San Francisco's Exploratorium.  Outside they had a large sheet metal wall with a pattern of holes.  Sparse spacing on the right blending to dense spacing on the left.  The wall faced the park and you could walk around to the other side beneath the cool shade of the eves.  Here, there were frosted glass "paddles" that were attached to strings.  You could pick up a paddle and hold it up to the pattern of holes and see small inverted image of the park eminating form each hole.  I remember being fascinated by the effect.  An image without a lens!

It wasn't until much later,
that the physics was explained to me.  I'd imagined being inside a dark room looking at a screen opposite a pinhole.  My friend was outside shining a flashlight at the hole.  As he moved up, then down, the image I saw moved down, then up.  It made sense why the image was inverted.

This same effect occurs naturally.
As the sun filters through the leaves, it normally creates round images.  Unless... There is an eclipse.  This image was made during May of 2012 when the moon crossed in front of the sun.  The normally round images were replaced by these crescents.  Natural imagery without a lens.   Pretty cool!