Question
a uranium mineral contains U-238 and Pb-206 in the ratio 4:1 by weight. Calculate the age of mineral (t½ for U-238 = 4.5 *10^9 years)
(a) 1.45*10^9 yrs
(b) 16.6*10^9 yrs
(c) 16.6*10^10 yrs
Joshi sir comment
U:Pb = 4:1
taking these ratio as mass
we get the initial mass of U = 4+(1*235/208)
and present mass of U = 4
now use the first order equation of radioactivity