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||You are trying to use the mirage effect, except that the
angle light gets bent via that effect is quite shallow. To
make light bend 90 degrees is likely to require a huge
amount of distance-traversal during the bending process.
||To what wavelength(s) is air not transparent?
||And, assuming that your laser is producing such a wavelength,
why won't it heat the air immediately in front of itself? Doesn't
this idea require the beam to pass through the firsr few metres of
air without absorbtion, then suddenly to start getting absorbed by
the next bit of air, near where the corner is? Why would the beam
behave like that?
||[pertinax] You could use an array of lasers that cofocalize at
a distance to warm air at one point. Then you could scan
the area ahead to create different densities of air. I saw an
image at wikipedia of three stacked fluids of different
refractive indices, so you could make sideways rather than
up and down heat layers.
||[Ian] I like your idea about hearing around corners with a
||Thank you. But ... but ... focus implies convergence. I thought
the rays that made up laser beams were approximately parallel,
neither diverging nor converging (maybe diverging a bit over very
long distances). Am I imagining that wrong?
||Yes. You are imagining a collimated laser beam. If you take
a laser diode out of an optical drive or a laser pointer, and
operate it with no lens, it will send light all over the place.
Some laser types (like the original ruby rod laser), I think,
naturally generate collimated beams, but they don't all. And
a collimated beam can be expanded and refocused using
lenses, just like any other beam of light can.