During a supernova, the outer layers of a star are blown off and the star's core shrinks down by a factor of 10,000 or more to form a neutron star. As the core shrinks, conservation of angular momentum says that

a. the core will spin faster.
b. the spin of the core does not change.
c. the core's rotational axis will precess rapidly, forming a pulsar.
d. the core will spin more slowly.

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