How fast can light change its direction?

Hello, John and Doves,

Here is a new/old thought on the idea of "twinkling."

How fast can light change its direction?

http://www.physicsforums.com/showthread.php?t=556126

The human eye is neither front-mirrored, nor rear-mirrored,

so any light reflecting off the surface of the eye is probably reflecting off

both the front and rear surfaces of a film of tears,

creating an occasional interference effect, driven by blinking and the redistribution of lachrymal fluid. This effect can be termed, "twinkling."

The question is, then, what is the speed of light through a typical film of tears?

First, we need a mathematical model:

[Report Number 11/11 Dynamics of the Tear Film

by Richard J. Braun, Oxford Centre for Collaborative Applied Mathematics,

Mathematical Institute, 24 - 29 St Giles’, Oxford OX1 3LB England]

"Why study the tear film that forms on the front of the eye every time we blink?

Within a very brief time post-blink, the ocular surface must establish a sufficiently

smooth outer surface through which we can see. The outermost surface is that

of the tear film. The tear film must provide a high-quality optical surface for

refraction, since it is the highest power interface in the ocular system (Oyster,

1999)." (excerpt from 1st page of the above document)

Let's look at the index of refraction, then:

Tear film thickness:

I hope I've made it abundantly clear that the twinkling of eyes

is much more problematic than, say, the twinkling of toes.

~Blessings,

Mike