Question

Carbon- 14 dating method is based on the fact that:
(A) Carbon- 14 fraction is same in all objects
(B) Carbon- 14 is highly insoluble
(C) Ratio of carbon- 14 and carbon- 12 remains constant during disintegration
(D) Carbon- 14 is highly soluble

Answer 1

Hint: To answer this question, you must recall the concept of radioactive decay of carbon- 14 isotope in a dead organic matter. Carbon- 14 is the heaviest of the three isotopes of carbon and it is radioactive in nature.

Complete step by step solution
Carbon- 14 is the radioactive isotope of carbon and is known as radiocarbon. It is a highly unstable species and undergoes radioactive decay unlike the stable isotopes of carbon- 12 and carbon- 13. Carbon- 14 is prepared in the atmosphere constantly due to the action of cosmic rays in the upper atmosphere on nitrogen atoms. The carbon- 14 thus formed oxidizes almost instantly in the air to form carbon dioxide gas and enters the carbon cycle.
This carbon- 14 isotope from the carbon dioxide is assimilated over a period of time in all plants and animals. When the plant or animal dies, the exchange of carbon with the atmosphere stops. The ratio of carbon- 12 isotope and carbon- 14 isotope in all living organisms is constant. When the organism dies, the level of carbon- 12 becomes constant while that of carbon- 14 decreases because of its radioactivity. By measuring, the ratio of carbon- 12 and carbon- 14 in a given sample and then comparing it to that in a living organism, the age of the sample can be determined.
The correct answer is C.

Note:
An isotope of an element is the species that has the same number of protons but a different number of neutrons. In other words, they are the atoms of the same element having a different mass. There are three isotopic forms of carbon, namely, carbon- 12, carbon- 13 and carbon- 14.