The half-life of Iodine - 131 is approximately 8 days, which means the mass of a sample of iodine decays by half every 8 days. The amount remaining can
be calculated using the formula i = 1600 * 2 ^ -t/8 , where t is the time in days since the beginning of the sample.
a) Write down this formula without negative exponents.
b)Find the amount of material remaining after 4 days as an exact and approximate value.
a) i = 1600 * 1/2^(t/8)
b) i = 1600 * 1/2^(1/2)
i = 1600 * 0.7071067812......
i =1,131.37 - grams remaining after 4 days(Exactly)
Since half-life is 8 days, it therefore means that in 4 days about 1/4 of 1600 would have decayed, or:
1600 - 400 = 1,200 grams (approx.) would remain after 4 days.