I find it humorous the way the CatoptricReflector1.jpg is
drawn in such a way that it is misleading with the light
rays not all coming at a 90 degree angle from the light
source.

Wayne Sallee
Wayne's Pets




Pszemol wrote on 6/19/2006 3:46 PM:
"Thomas Bartkus" wrote in message
. ..
"Steve" wrote in message
...
On Mon, 19 Jun 2006 07:14:46 -0500, "Pszemol"
wrote:

This is agains the physics of light reflection theory.
Majority of light will be reflected from the water surface
and hits the walls, suffit of your room.

Are you saying that the beam needs to be vertically down at 90 deg to
the water surface for good efficiency? I was not aware that there
would be huge differences,

I don't know if he's saying that or not. But it would be wrong. You
can't
really "beam vertically down" because you don't have a coherent beam.
It's
not a laser. You have an immense multiplicity of "beams" leaving the
fixture at every possible angle. You might get a small increase in
perpendicular "beams" striking the surface if set the reflector
vertically.
But it is unlikely to be by much.

Well, the goal in building a good lamp fixture is to aim
as much light as possible going stright from the lamp...
Not at the angle.
The goal is achived by making a source of light as small
as posible, being close to the point source, and to place
this light source in the focal point of the parabolic reflector...

And this is not a problem it is not a laser.
We do not care if the beam is coherent or not...
We do not care even for light to be monochromatic, since
the reflection ratio or the angle of the polished aluminium
reflector is pretty much the same for any color...

What is the problem in an ordinary lamp is the light source
which is not an ideal point source but usually a quite large
bright spot.
In case of HQI lamp it will be this electric arc in the
ceramic bulb of the size of 1/2" or so... and this is much
easier to focus than the light coming from a fluorescent tube.

If we could get a point source of light and place it directly in
the focal point of ideal parabolic reflector we would get a nice
beam of parallel rays of light coming out of the lamp fixture...

Basic principle is shown on the picture below:
http://www.btinternet.com/~k.trethew...ng_systems.htm