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inysia [295]
3 years ago
7

A paleontologist estimates that when a particular rock formed, it contained 12 mg of the radioactive isotope potassium-40, which

has a half-life of 1.26 billion years. The rock now contains 3 mg of the isotope. About how old is the rock? Enter in billions of years.
Physics
1 answer:
leva [86]3 years ago
7 0

Answer:

t = 2.52 billion \:years

Explanation:

As we know by radioactivity law

N = N_o e^{-\lambda t}

so here we will have

N = 3 mg

N_o = 12 mg

now we will have

3 = 12 e^{-\lambda t}

\lambda t = ln 4

now we also know that

\lambda = \frac{ln2}{1.26 \times 10^6 yrs}

t = 1.26\times 10^6\times \frac{ln4}{ln2}

t = 2.52 billion \:years

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