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### Solar Concentrator

Posted: Tue Feb 06, 2007 1:10 am
I intend to construct a large parabolic reflector made of Mirrors, plywood, Acrylic Ball Joints, Etc. What I wish to ask is some sort of way that I can correctly measure the angles for a focal point, maybe 6 in- 2 ft away from the central mirror. Any Ideas?

Posted: Tue Feb 06, 2007 4:06 am
If you do a search in Wikipedia on parabola, you will come up with the mathematical formulas for the focus point of parabolas.

http://en.wikipedia.org/wiki/Parabola

We're not sure what grade you are in, but the formulas have mostly been simplified to algebra, and aren't that difficult.

Hope this helps.

Alternatively, you can build a parabola and check the focus point by pointing a laser pointer at it, but be careful that you cannot accidentally be looking straight at the laser, which can permanently hurt the retina in your eyes. I would use that as a plan B.

Posted: Tue Feb 06, 2007 8:54 am
zzzzdoc wrote:If you do a search in Wikipedia on parabola, you will come up with the mathematical formulas for the focus point of parabolas.

http://en.wikipedia.org/wiki/Parabola

We're not sure what grade you are in, but the formulas have mostly been simplified to algebra, and aren't that difficult.

Hope this helps.

Alternatively, you can build a parabola and check the focus point by pointing a laser pointer at it, but be careful that you cannot accidentally be looking straight at the laser, which can permanently hurt the retina in your eyes. I would use that as a plan B.

If you do use a laser pointer, use a red one, not a green one. Also, the cheaper the laser pointer, the less bright it is (generally).

Louise

Posted: Tue Feb 06, 2007 9:32 am
The laser pointers are also labeled as to which class of power they emit. The lower/lowest, the better.

You should try to catch a rerun of the Mythbusters episode where they made the Archimedes Death Ray (there are actually 2 episodes, the original, and the one where the guys from MIT come down to melt one for Big Gray.)