A certain radioactive element has a half-life of 1 hour. If you start with a 1-g sample of the element at noon, how much of this same element will be left at 3:00 pm? (a) 0.5 g (b) 0.25 g (c...

A certain radioactive element has a half-life of 1 hour. If you start with a 1-g sample of the element at noon, how much of this same element will be left at 3:00 pm?

(a) 0.5 g

(b) 0.25 g

(c) 0.125 g

(d) 0.0625 g

The isotope cesium-137, which has a half-life of 30 years, is a product of nuclear power plants. How long will it take for this isotope to decay to about one-half its original amount?

(a) 0 yr

(b) 15 yr

(c) 30 yr

(d) 60 yr

(e) 90 yr