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Re: [Phys-l] fire starter from the sun - revisited



A gross of 1-foot-square mirror tiles. That would be 144 square feet.
How well could these be aimed? If you could get them all pointed at the
same square-foot of target, no small feat, the solar concentration would
be 144:1.

Now take a 100-mm diameter f/2 magnifying glass. The area is 7850 mm^2
and the minimum solar spot would be a diameter of 1.86 mm which would be
an area of 2.72 mm^2. This solar concentration would be 7850:2.72 which
reduces to 2880:1. That would be about 20 times more concentrated than
the gross of mirrors if you could actually get all the mirrors aimed at
the same 1-ft^2 of target. It would appear to me you would need a few
thousand 1-foot mirrors to have any hope of reaching the temperature of
a 100-mm f/2 lens, and that assumes the holders could keep them aimed
onto a one-foot spot.


Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu