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me that a particular radioactive-isotope decay has a half-life of 100 million ye

ID: 115618 • Letter: M

Question

me that a particular radioactive-isotope decay has a half-life of 100 million years. Also 21. Assu assume that the parent isotope is incorporated into the minerals found in igneous rocks and that the only daughter atoms in the rock formed from the decay of the parent isotope. Measurements show that one mineral in the igneous rock contains 5 million atom million atoms of daughter. s of the parent isotope and 35 (a) What is the age of this mineral in years? Show your math calculations here. (b) What is the age of the rock? Explain how you determined your answer.

Explanation / Answer

a) given,

ND= 35 *106

Np= 5*106

No= ND+Np= 40 *106

t1/2= 100*106

N=N0e-.693/t1/2*tf

tf= 130*106years

age of the mineral is 130 million years

b) age of the rock is also 130 million years as the it only becomes a closed system when rock is formed . this is the basic assumption that we take.