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Find the half-life of a certain radioactive substance which decays according to the formula 𝑦 = ,
where y is the amount present after t years?
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The initial mass is 100 units at t= 0.
At the half-life value of t, the remaining mass is = 50.
So we write the decay equation in ekt-form
50 =
=
0.5 =
Take logarithm base "e" (natural logarithm) of both sides
ln(0.5) = -3t
Express "t" and calculate
t = = 0.231049 years. ANSWER
CHECK. = = use your calculator = 50.0000 ! precisely correct !
Solved.
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- Radioactive decay problems
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The referred lesson is the part of this online textbook under the topic "Logarithms".
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