The mineral monazite is a rich source of thorium, available in large quantity in kerala. A typical monazite sample contains 9% ThO_(2) and 0.35% U_(3)O_(8). .^(208)Pb and .^(206)Pb are the stable end products in the radioactive decay series of .^(232)Th and .^(238)U respectively. All the lead in monazite is of radiogenic origin. The isotopic ratio of .^(208)Pb//^(232) Th. was found to be 0.104. The half lives of Th and U are 1.41 xx 10^(10) years adn 4.47 xx 10^(9) years respectively. The time elapsed since the formation of monazite sample will be:

The mineral monazite is a rich source of thorium, available in large q

1.	The mineral monazite is a rich source of thorium, available in large quantity in kerala. A typical monazite sample contains 9% ThO_(2) and 0.35% U_(3)O_(8). .^(208)Pb and .^(206)Pb are the stable end products in the radioactive decay series of .^(232)Th and .^(238)U respectively. All the lead in monazite is of radiogenic origin. The isotopic ratio of .^(208)Pb//^(232) Th. was found to be 0.104. The half lives of Th and U are 1.41 xx 10^(10) years adn 4.47 xx 10^(9) years respectively. The time elapsed since the formation of monazite sample will be:
Answer» `1.34 xx 10^(9)` years `2.01 xx 10^(9)` years `1.41 xx 10^(9)` years `4.47 xx 10^(9)` years Solution :`(0.693)/(t_(1//2)Th) = (2.303)/(t_("AGE")) log ((N_(0))/(N))` `(0.693)/(1.41 xx 10^(10)) = (2.303)/(t_("age")) log (1.104)` `t_("age") = 2.01 xx 10^(9)` years