A freshly prepared radioactive material has an half life 2 years.It emits radiaion which is 64 times the permissibile safe level dose.The min. time after which it would be possible to work safely with the source is_____________

Let the permissible radiation level be K. Current emission is 64K

In 2 years, it will emit 32K

In 4 years, it will emit 16K

in 6 years, it emits 8K

and so on

In 12 years, the sample will emit radiation at level K, which is suitable for work

half-life period = 2 yrs

since it emits 64 times the permissible level

time after which it works safrly is : 2ⁿ=64

n=6 half lifes

so, after 12 years , its safe to work with radioactive material

---

Please feel free to post as many doubts on our disucssion forum as you can. If you find any question difficult to understand - post it here and we will get you the answer and detailed solution very quickly. We are all IITians and here to help you in your IIT JEE preparation. All the best.

Regards,
Naga Ramesh
IIT Kgp - 2005 batch