Question

Carbon- 14 dating method is based on the fact that (a) C-14 fraction is same in all objects (b) C-14 is highly insoluble (c) ratio of carbon- 14 and carbon-12 is constant (d) all the above

Short answer

The correct answer is (c): ratio of carbon-14 and carbon-12 is constant.

Step-by-step solution

Understanding Carbon-14 Dating

Carbon-14 dating is a method used to determine the age of an object containing organic material by measuring the amount of carbon-14 it contains. This relies on the assumption that the ratio of carbon-14 to carbon-12 in the atmosphere is relatively constant over time.

Identify the Premise of Carbon-14 Dating

The key premise for carbon-14 dating is that living organisms incorporate carbon-14 into their bodies at a constant ratio with carbon-12, because this ratio is fixed in the atmosphere during the organism's lifespan.

Evaluating Each Option

- Option (a): 'C-14 fraction is same in all objects' is incorrect because the C-14 fraction changes over time in dead organisms. - Option (b): 'C-14 is highly insoluble' is irrelevant to the dating method. - Option (c): 'ratio of carbon-14 and carbon-12 is constant' is directly linked to the method's accuracy as it assumes the atmospheric ratio is constant.

Choosing the Correct Option

From our evaluation, option (c) is the correct one, as it aligns with the scientific basis for carbon-14 dating. The key feature of carbon dating is that it presumes a constant ratio of C-14 to C-12 in the atmosphere, which living organisms maintain while alive.

Key concepts

Carbon-14 and Carbon-12 Ratio

Carbon-14 is a radioactive isotope of carbon that is used in carbon dating. This technique is founded on the principle that the ratio of carbon-14 to carbon-12 in the atmosphere remains consistent over long periods. Living organisms, through their respiration and intake of carbon, maintain this carbon ratio while they are alive. The idea is simple but fundamental; they absorb both isotopes equally from the atmosphere through processes such as eating and breathing. Once the organism dies, it stops taking in carbon.

• This leads to a gradual decay of carbon-14, while carbon-12 remains stable.
• The decay process of carbon-14 results in a lowering of its concentration compared to carbon-12.
• By measuring how much carbon-14 remains in a sample and comparing it to carbon-12, scientists can estimate how long it has been since the organism died.

The constancy of the carbon ratio in the atmosphere is key to this dating method's accuracy. Any changes in this ratio over time can lead to inaccuracies if not accounted for in the calculation. Calibration curves have been developed based on many years of data, helping to refine these estimations further.

Radiometric Dating Techniques

Radiometric dating is a broad category of methods used to determine the age of materials by studying natural radioactive decay. Carbon-14 dating is one such specific method within this broader category, tailored for organic materials.
Multitudes of different elements have isotopes that can be used for radiometric dating. All these methods rely on the concept of half-life, which is the time it takes for half of a given isotope sample to decay.

• The choice of which isotope to use depends on the type of sample and the timescale needed.
• For instance, uranium-lead dating is often used for dating rocks billions of years old.
• In all these methods, measuring the remaining amount of a radioactive isotope allows scientists to calculate when the material stopped exchanging atoms with its surroundings, usually the point when the object ceased to be "alive."

Among these methods, carbon-14 remains popular for archaeologists when dating recent artifacts and organic remains, such as wood, bones, and shells.

Age Determination of Organic Materials

Determining the age of organic material using carbon-14 dating involves several intricate steps. Once a living organism dies, the carbon-14 it contains begins to decay. Scientists measure the amount of carbon-14 left in a specimen and compare this with its stable counterpart, carbon-12, to determine age.

Key Steps in the Process:

• Sample Collection: Care is taken to prevent contamination, which might skew the age measurements.
• Measurement: The ratio of carbon-14 to carbon-12 is determined, often using a mass spectrometer.
• Calculation: Based on the known half-life of carbon-14, approximately 5,730 years, the time since death can be estimated.

This calculation assumes that the initial carbon-14/carbon-12 ratio matches the present atmospheric ratio. This is why understanding atmospheric variations over time is crucial. Thus, carbon dating offers a remarkable tool for historical and archaeological studies, providing insights into events up to 50,000 years old.