What is the phenomenon called when light is bent due to
heat (ie those waves you "see" over your bbq grill or behind a jet engine?
The phenomenon is called refraction. This is due to the differences of the
index of refraction due to temperature differences in the air. On a large
scale, you can get a mirage.
There is a special type of photography called schlieren where regions of
varying refraction in a transparent medium (usually temperature or pressure
differences) are detectable. They are photographed by passing light through
---Nathan A. Unterman---
It's called refraction. The bending of light isn't intrinsically due to
heat; it's because the hot air above your grill, or in a low spot in a
road, is less dense than the surrounding air. The speed of light is
different in these two bodies of air (slower in the denser medium), and the
light bends toward the denser medium.
Richard Barrans Jr., Ph.D.
This is refraction, just like with a glass lens. The hot air over the grill
(behind the engine) is less dense than the rest of the air. The light travels
at a different speed through the less dense air than it does in the more dense
(normal) air. This results in bending the light.
It is called the refraction of light or bending of light due to a change in
medium (what the light is traveling through). The heated air has a
different "density" then the air around it so the light rays bend as they
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Update: June 2012