A radioactive substance decays exponentially Let Q0 be the i

A radioactive substance decays exponentially. Let Q_0 be the initial amount of the substance. Q(t) the amount after t days. The substance decays to 25% of the initial amount after 9 days. What is the half-life of the substance? Explain!

Solution

Concentration after 9 days is 1/4 of initial concentration,in one half life concentration become half,so time required is two half lives.

2. Half lives equal 9 days

So one half life equal 4.5 days.