|Jul29-06, 08:44 AM||#1| Question on light intensity at the
focus of a lens. From using a magnifying lens under the Sun, I
gather it can focus all or most of the light impinging on its
surface area to a small spot and that is how it is able to
create a greater intensity light at its focus (disregarding
absorption in the lens.) Correct? What portion of the total
light falling on the lens would be delivered to the focal spot
ignoring absorption? This would be true no matter how far away
the focal point. So the normal dimunition of intensity by the
square of distance would not apply. So for example if you had a
lens of focal distance 1 AU and put this lens right next to the
Sun and directed the lens to shine toward the Earth, the full
intensity of the Sun at its surface could be delivered to the
Earth. True? In a more realistic scenario if you put the lens
some ten to hundreds of thousands of kilometers away from the
Sun's surface so it could survive the heating then the intensity
delivered to the Earth would st