Question

A human body excretes ( removes by waste discharge sweating etc.) certain materials by a law similar to radioactivity. if technitium is injected in some form in a human body.the body exerts half - the amount in 24hours . A patient is given an injection containing $$ ^{99}tc $$ this isotope is radioactive with a half-life of 6 hours.the activity frim the body just after the injection is $$ 6 \mu Ci $$ How much time will elapse before the activity falls to $$ 3 \mu Ci $$?

Answer 1