Corals take up certain elements from seawater, including uranium but not thorium. after the corals die, the uranium isotopes slowly decay into thorium isotopes. a measurement of the relative fraction of certain isotopes therefore provides a determination of the coral's age. a complicating factor is that the thorium isotopes decay as well. one scheme uses the alpha decay of ^{234}\rm u to ^{230}\rm th . after a long time, the two species reach an equilibrium in which the number of ^{234}\rm u decays per second (each producing an atom of ^{230}\rm th ) is exactly equal to the number of ^{230}\rm th decays per second.
1.what is the relative concentration of the two isotopes - the ratio of ^{234}\rm u to ^{230}\rm th - when this equilibrium is reached?