A piece of fossilized wood has a carbon-14 radioactivity that is 1/4 that of new wood. The half-life of carbon-14 is 5730 years. How old is the cloth?

What fraction of a radioactive sample has decayed after two half-lives have elapsed?

If a 1.50cmthick piece of lead can absorb 90.0% of the rays from a radioactive source, how many centimeters of lead are needed to absorb all but 0.100% of the rays?

Natural uranium consists of 235U(percent abundance = 0.7200%, =3.121017/s ) and 238U (percent abundance = 99.27% , =4.921018/s ). What were the values for percent abundance of 235Uand 238Uwhen Earth formed 4.5109years ago?