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The surface temperature of the sun is approx. 5700 deg C, the diameter is approx. 1.4 million km, the earth sun distance is approx. 150 million km. The highest temperature that you can achieve on earth by any known optical means is something a bit less than 5700 deg. C. the size of the image that you can focus on earth is the diameter of the sun divided the ratio the two focal distances at play here. The, a bit lessedness than 5700 deg. C is the efficiency of the lens over the f ratio of the lens. (I think?)
1.4*10^6/150*10^6= 9.4 mm
for 1m focal length @ f10 the temperature would be approx. 80 percent of 570 degrees
0.8*5700/10=456deg. C.
For .1m focal length @f1 the spot will be .94mm at a temp. of 4,569 deg. C.
For 1m @f1, the spot = 9.4mm at 4,569 deg. C
I think I may have stuffed up somewhere on the role of the f factor, but you can see my line of reasoning for at least the spot size and temperature part of the problem.
Last edited by bgilbert; 21-12-2019 at 06:13 PM.
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