Physics Help Forum Radioactive decay problem

 Nuclear and Particle Physics Nuclear and Particle Physics Help Forum

 Feb 26th 2009, 03:12 PM #1 Junior Member   Join Date: Feb 2009 Posts: 2 Radioactive decay problem The chapter we are on is Radioactive Decay and the Nucleus. Here is the question: There are 600 g of radioactive iodine-133. The half life of iodine-133 is 21 h. a) How much of this radioactive substance would exist after 21 h. ? b) After 42 h. ? c) After 126 h. ? P.S. If you could explain how to do this and maybe show me how to work this problem out, I would appreciate it! - Confused
 Feb 26th 2009, 06:12 PM #2 Senior Member   Join Date: Dec 2008 Location: Las Cruces NM Posts: 256 For example, 126 = (6)(21) so the amount left after 126 hours is $\displaystyle \frac {600}{2^6} = \frac{600}{64}$.
 Jul 27th 2009, 09:49 PM #3 Physics Team     Join Date: Jul 2009 Posts: 310 Decay equation: $\displaystyle m = m_o(\frac{1}{2})^{\frac {\Delta T}{T_{half}}}$ $\displaystyle m_o$ is intial mass $\displaystyle \Delta T$ is change in time $\displaystyle T_{half}$ is the half-life time interval $\displaystyle m$ is the mass remaining. All you gotta to do now is substitute. __________________ "Dissent is the highest form of patriotism." - Thomas Jefferson. "Give me control of a nation's money and I care not who makes her laws." -Mayer Amschel Rothschild I study Mathematical Physics at the University of Waterloo. -DC
Jul 28th 2009, 08:30 PM   #4
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 Originally Posted by Deco Decay equation: $\displaystyle m = m_o(\frac{1}{2})^{\frac {\Delta T}{T_{half}}}$
It's easier to read if you write it as follows

$\displaystyle m = m_o 2^{-\frac {\Delta T}{T_{half}}}$

 Jul 28th 2009, 08:32 PM #5 Physics Team     Join Date: Jul 2009 Posts: 310 Whatever floats your boat. __________________ "Dissent is the highest form of patriotism." - Thomas Jefferson. "Give me control of a nation's money and I care not who makes her laws." -Mayer Amschel Rothschild I study Mathematical Physics at the University of Waterloo. -DC
Jul 28th 2009, 08:33 PM   #6
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 Originally Posted by Deco Whatever floats your boat.
Usually water.

 Jul 28th 2009, 08:37 PM #7 Physics Team     Join Date: Jul 2009 Posts: 310 Hehe. . __________________ "Dissent is the highest form of patriotism." - Thomas Jefferson. "Give me control of a nation's money and I care not who makes her laws." -Mayer Amschel Rothschild I study Mathematical Physics at the University of Waterloo. -DC
Jul 28th 2009, 08:45 PM   #8
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 Originally Posted by Deco Hehe. .
I only mentioned it because the way Latex comes out it looks funny. It took me a few seconds for my eyes to adjust to what the expression was. Writing it in terms of exponentiating 2 makes it easier on my eyes and if its easier on my eyes there's a good chance its easier on others eyes too