PH 122 Lecture Notes - Special Relativity, Becquerel, Radium
Document Summary
There are two main isotopes of uranium, 235u and 238u. Two billion years ago, 235u comprised 3% of the uranium in the earth"s crust. Now, it"s prevalence has dropped to 0. 7% of the uranium in the earth"s crust. Use the quick and dirty form of mass m (226ra) = 226 u = 3. 75 x 10-25 kg. 3. 75 x10 25kg per atom = 2. 67 x 1021 atoms (226ra) = 1600 yr = 5. 05 x 1010 s m = t 1. R = 3. 7 x 1010 bq = 1. 0 ci. My watch has a tritium ( t 1. When i purchased it in 2004, it had an activity of about 100 mbq. R = 100 mbq [ ]10 yr/12 yr. A scrap of parchment from the dead sea scrolls was found to have a 14c/12c ratio that is. 2 ln . 795 = ln t/5730 yr t = 1900 years.
