Question

if the half life of uranium 232 is 70 years how many half lives will it take for 10 grams of it to be reduced to 1.25 grams​

Answer 1

Given :

The half life of uranium 232 is 70 years.

To Find :

How many half lives will it take for 10 grams of it to be reduced to 1.25 grams​.

Solution :

We know, formula of radioactive decay is :

`(N)/(N_o)=((1)/(2))^n`

Here,
`N_o` is initial amount and N is remaining amount.

Putting all given values in above equation, we get :

`((1)/(2))^n = (1.25)/(10)\\\\((1)/(2))^n = (1)/(8)\\\\n = 3`

Therefore, it takes 3 half lives i.e. 210 years to reduced to 1.25 grams.