Sample question (2000)
•Q. As every scout
knows, you can start a fire on
a sunny day by holding a magnifying glass between the sun and a piece of paper placed on the ground.
–Is the radiance of
the sun as seen from the focal point
of the lens more, less, or the same as the radiance as seen from the same point in the absence of the magnifying glass?
–Is the irradiance
due to the sun at the focal point more,
less, or the same as the irradiance at the same point in the absence of the magnifying glass?