Than a cool
FIGURE 2
Apparent and Absolute Brightness
The three stars Alnitak, Alnilam, and
Mintaka in the constellation Orion all
seem to have the same apparent bright-
ness from Earth. But Alnilam is actually
farther away than the other two stars.
CHALLENGE Which star has the
greatest absolute brightness? How do
you know?
30 points

With the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 1.90