Matt Giwer wrote:
>
> "SamuelT." wrote:
>
> > When I read this statement of yours I immediately thought of mirages. I
> > wonder if mirages are caused in part to this natural effect?
>
> Yes. It is a total reflection angle that is dependent upon the
> IOR of what is reflecting it. Air near the ground is hotter,
> decreasing its IOR.
I forgot about this discussion.
At some critical (shallow) angle there is "total" reflection.
Debating total is left to the purists. There is also refraction
agreed.
Now as to the mirage case ...
The total reflection plane is the closest to the ground. That is
why it look blue because it is reflecting the sky. Above that is
the refraction area. As it is rising heat, there is turbulence.
That is what makes the reflected sky appear to ripple and thus
appear to be water -- a fashion only a person desperate for water
would imagine. Also note the critical angle surface is also
rising heat so it is also turbulent and will contribute to the
water-like appearance.
Generally we are familiar with a critical angle for water and
glass. The critical angle is dependent upon the difference in
IORs for the media. The less the difference, the shallower the
angle and the further away the mirage water appears to be.
In the mirage case we are not dealing with our usual experience
with water and glass but with a material with a turbulent
boundary. We have both refraction and reflection at work. What we
can say is that refraction is in play higher than the reflection
height but we can not see refraction effects below that
reflection height.
This is the sort of thing that makes physics fun. It is
separating two phenomena and they seeing how they interact.
Newton's first law of motion (stay in motion) would have been
known to cavemen were it not for friction. Once motion and
friction were split there was progress.
--
http://www.giwersworld.org/artiii/
Oh my God! They've rendered Kenny!
How to profit from the end of civilization as know available here
soon.
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