Really? I thought the argument has settled in to the temperature of the
image. Again, starting a fire depends on properties of the target.
Concentrating a superfine image of the sun on a thin piece of straw will
vaporize it without starting a fire in adjacent regions. A cruder lens that
warms a larger area more slowly would be better at getting the combustion to
spread. I use the sighting lens on my orienteering compass to start fires -
I can assure you it's not diffraction limited.
Sorry if I got OT.
Bob at PC
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Edmiston,
Mike
Sent: Tuesday, April 25, 2006 2:58 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] fire starter from the sun - revisited
Bob at PC said, "Depends on the desired result - if you are boiling a
large pot of water, the mirrors are better (surface area) - if you are
trying to quickly burn the wings off a bug without killing it, then a
100 mm diameter lens might be better."
I thought we were trying to start a fire. Seems like that's in the
subject line of the thread.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu