Calculating Radiation Emitted from K-40?

[ampzor]

How would I be able to calculate the amount of microcuries of radiation emitted from 3 grams of K-40? I think I have a way of figuring it out but it is pretty lengthy and I am sure that I am over thinking this a bit too much.

 

[Bob S]

The half life of K-40 is 1.277 x 10⁹ years = 4.03 x 10¹⁶ seconds. The half life is Ln(2) = 0.693 x the 1/e lifetime. So the 1/e lifetime is about 5.81 x 10¹⁶ seconds.

3 grams of K-40 contains (3/40) x 6.02 x 10²³ = 4.51 x 10²² atoms.

There are about 4.51 x 10²²/5.81 x 10¹⁶ = 7.76 x 10⁵ dps (decays per second) in 3 grams of K-40..

1 Curie = 3.7 x 10¹⁰ dps.

Bob S

 

[minerva]

The specific radioactivity per unit mass for a particular radionuclide, measured in Ci/g or Bq/g for example, is more commonly known as the "specific activity". Whilst you can calculate it from first principles if you know the half-life, as elucidated above, usually you just look up the specific activity of whatever radionuclide you're working with in literature tables.

 

[ampzor]

Thank you Bob S.

 

[techocharles]

does anyone know if the http://iphonecarmount.org" gives out radiation?