pookiebear
New member
The primary mirror of a certain telescope has a total area of 2.8 square meters for its aperature. The mirror focuses incoming light down to an image area of .00064 square meters. If the light from a celestial object exhibits an apparent brightness of .000000000004 watts/square meter as it strikes the primary mirror, what brightness in watts/square meter will be observed at the focal point of the telescope? Assume that all of the light which initially strikes the primary mirror ends up at the focal point.