Dose rate calculation: 20 mSv per hour at 10 micrometres

Kyebas

New member
I just want to know the formula for the following question:

If the dose rate from a sample of Ra-223 was found to be 20 mSv per hour at 10 micrometres, calculate the dose rate at 30 micrometres. Show your calculations. Give your answer to one decimal place

I think it is 20 mSv x 10 micrometres / 30 micrometres, but I am not sure if I have to convert to metres or not (if not I get 6.6).

Dr.Peterson

Elite Member
I just want to know the formula for the following question:

If the dose rate from a sample of Ra-223 was found to be 20 mSv per hour at 10 micrometres, calculate the dose rate at 30 micrometres. Show your calculations. Give your answer to one decimal place

I think it is 20 mSv x 10 micrometres / 30 micrometres, but I am not sure if I have to convert to metres or not (if not I get 6.6).
You will need physics, not just math, to determine the formula. Have you been taught how radiation doses relate to distance?

I would expect it to follow an inverse square law, meaning that the dose is inversely proportional to the square of the distance. If that is so, then you should use that proportionality to solve the problem. Conversion of units is not needed, since units of distance are the same.