Half life

1
Half life

• Exponential functions

2
Half Life
Definition Half-life- the time it takes
for one-half of the atoms of an unstable
element or nuclide to decay radioactively into
another element or nuclide.
3
Radium has a half life of 1600 years. If A0
8 grams, show that the decay function for the
mass remaining after n years is given by
Use this function to find the mass left after
(i) 40 years (ii) 200 years
4
A radioactive element has a half life of only
20 years. Write down a decay function for 40
grams of the material after n years. a)
Calculate the mass left after 15 years. b)
Calculate the mass left after 45 years.
5
The half life of C14 the radioactive form of
carbon is 5730 years. If 5 gram of carbon is
initially present, construct a decay function
that models the amount left after n years. How
much will be left after 10000 years?
6
The table shows some materials, their half lives
and their area of application.
Use this table to answer the questions on the
next slide.
7
For each material set up a decay function for
50 grams of the material. Use these decay
functions to answer the following questions. How
much Iodine 123, is left after 1 day? How much
Cobalt -60, is left after 8 years? How much
Plutonium-239, is left after 1000 years?