Question

Half-life period of $U^{237}$ is $2.5\times {10}^5$years. In how much time will the amount of $U^{237}$ remaining be only $25$% of the original amount?

• A. $2.5\times {10}^5$ years
• B. $1.25\times {10}^5$ years
• C. $5\times {10}^5$ years
• D. ${10}^6$ years

Answer 1

Answer: (C)

$5\times {10}^5$ years

In two half time it remains 25% only.

So, time taken, $t=2\times 2.5\times {10}^5=5\times {10}^5$ years