1
Question
Consider following statements
I. 'Carbon-dating' is based on the measurement of the activity of 14C.
II. 40K is used to determine the age of the objects up to 1 million years old.
III. The uranium-lead method is based on the natural uranium-238 decay series which ends up with the production of stable lead-206.
Select the correct statements:
Consider following statements
I. 'Carbon-dating' is based on the measurement of the activity of 14C.
II. 40K is used to determine the age of the objects up to 1 million years old.
III. The uranium-lead method is based on the natural uranium-238 decay series which ends up with the production of stable lead-206.
Select the correct statements:
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Solution
The correct option is D I, II, III
Potassium-Argon dating:
The element potassium (symbol K) has three nuclides, K39, K40, and K41. Only K40 is radioactive; the other two are stable. K40 can decay in two different ways: it can break down into either calcium or argon. The ratio of calcium formed to argon formed is fixed and known. Therefore the amount of argon formed provides a direct measurement of the amount of potassium-40 present in the specimen when it was originally formed.
Because argon is an inert gas, it is not possible that it might have been in the mineral when it was first formed from molten magma. Any argon present in a mineral containing potassium-40 must have been formed as the result of radioactive decay. F, the fraction of K40 remaining, is equal to the amount of potassium-40 in the sample, divided by the sum of potassium-40 in the sample plus the calculated amount of potassium required to produce the amount of argon found. The age can then be calculated from equation.
Carbon Dating: Radiocarbon, or carbon 14, is an isotope of the element carbon that is unstable and weakly radioactive. The stable isotopes are carbon 12 and carbon 13.
Carbon 14 is continually being formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen 14 atoms. It is rapidly oxidized in air to form carbon dioxide and enters the global carbon cycle.
Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes. When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.
Radiocarbon dating is essentially a method designed to measure residual radioactivity. By knowing how much carbon 14 is left in a sample, the age of the organism when it died can be known. It must be noted though that radiocarbon dating results indicate when the organism was alive but not when a material from that organism was used.
From Uranium 238 to Lead 206, the instability caused by the alpha decay is corrected by the eventual beta decay, leading to the stable nucleus of lead 206.
The element potassium (symbol K) has three nuclides, K39, K40, and K41. Only K40 is radioactive; the other two are stable. K40 can decay in two different ways: it can break down into either calcium or argon. The ratio of calcium formed to argon formed is fixed and known. Therefore the amount of argon formed provides a direct measurement of the amount of potassium-40 present in the specimen when it was originally formed.
Because argon is an inert gas, it is not possible that it might have been in the mineral when it was first formed from molten magma. Any argon present in a mineral containing potassium-40 must have been formed as the result of radioactive decay. F, the fraction of K40 remaining, is equal to the amount of potassium-40 in the sample, divided by the sum of potassium-40 in the sample plus the calculated amount of potassium required to produce the amount of argon found. The age can then be calculated from equation.
Carbon Dating: Radiocarbon, or carbon 14, is an isotope of the element carbon that is unstable and weakly radioactive. The stable isotopes are carbon 12 and carbon 13.
Carbon 14 is continually being formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen 14 atoms. It is rapidly oxidized in air to form carbon dioxide and enters the global carbon cycle.
Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes. When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.
Radiocarbon dating is essentially a method designed to measure residual radioactivity. By knowing how much carbon 14 is left in a sample, the age of the organism when it died can be known. It must be noted though that radiocarbon dating results indicate when the organism was alive but not when a material from that organism was used.
From Uranium 238 to Lead 206, the instability caused by the alpha decay is corrected by the eventual beta decay, leading to the stable nucleus of lead 206.
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