Question

Which of the following option is correct? (a) In living organisms, circulation of \({ }^{14} \mathrm{C}\) from atmosphere is high so the carbon content is constant in organism. (b) carbon dating can be used to find out the age of earth crust and rocks (c) radioactive absorption due to cosmic radiation is equal to the rate of radioactive decay, hence the carbon content remains constant in living organism (d) carbon dating can not be used to determine concentration of \({ }^{14} \mathrm{C}\) in dead beings.

Short answer

Option (c) is correct; in living organisms, radioactive absorption equals decay rate, stabilizing carbon content.

Step-by-step solution

Understanding Carbon in Living Organisms

Living organisms constantly exchange carbon with the atmosphere through processes like respiration and photosynthesis. Option (a) suggests that the circulation of carbon-14 from the atmosphere is high, but what keeps carbon content consistent during life is not the circulation rate, but the constant exchange with the environment.

Analyzing Carbon Dating Usefulness

Carbon dating is primarily used to determine the age of once-living materials based on the decay rate of carbon-14. Since rocks and the earth's crust are not made from organic material, option (b) is incorrect because it suggests using carbon dating for non-organic materials, which is not its intended use.

Radioactive Equilibrium in Living Organisms

In living organisms, the rate of absorption of carbon-14 from the environment due to cosmic radiation is roughly equal to its decay rate, keeping the carbon-14 content stable while the organism is alive, which makes option (c) correct.

Evaluating the Application of Carbon Dating

Option (d) states that carbon dating cannot determine the concentration of carbon-14 in dead beings, which is incorrect. Carbon dating is specifically used to measure the concentration of carbon-14 to estimate the time since death, as this concentration decreases with time.

Key concepts

Carbon-14 Decay

Carbon-14 is a radioactive isotope of carbon, known for its role in dating organic materials. It is formed in the upper atmosphere when cosmic rays interact with nitrogen atoms. Once formed, carbon-14 spreads across the atmosphere and is absorbed by living organisms through natural processes like respiration and photosynthesis.
The essence of carbon-14 decay lies in its predictable nature. Over time, carbon-14 decays into nitrogen-14 at a steady rate. This rate is expressed in terms of half-life, which is the time it takes for half of the carbon-14 in a sample to decay. The half-life of carbon-14 is about 5,730 years.
The predictable decay process is key for dating, as it allows scientists to backtrack and calculate how long ago the organism stopped absorbing carbon-14, i.e., when it died. Hence, understanding carbon-14 decay is fundamental when utilizing carbon dating techniques to estimate the age of organic objects.

Radioactive Equilibrium

In living organisms, a state of radioactive equilibrium is maintained where the rate of carbon-14 uptake equals the rate of its decay. This dynamic balance is crucial for ensuring that the carbon-14 content within an organism remains fairly stable throughout its life.
This equilibrium is disrupted once the organism dies. After death, the uptake of carbon-14 ceases, and the isotope begins to decay without replacement. Knowing this balanced state exists during life is crucial since it forms the basis for calculating how much carbon-14 should originally have been present compared to what remains at a certain point after death.
Maintaining radioactive equilibrium in living organisms signifies the natural regulatory processes that keep carbon levels consistent, highlighting how cosmic radiation's continuous interaction with the atmosphere plays a pivotal role in these natural cycles.

Organic Material Dating

Carbon dating, also known as radiocarbon dating, is a widely used method for determining the age of organic materials. This technique measures the amount of carbon-14 remaining in a once-living object, allowing scientists to estimate how long it has been since the organism's death.
This method is effective for dating organic materials up to about 50,000 years old, thanks to carbon-14's relatively short half-life. It is particularly useful in archaeology and geology for dating artifacts, bones, and remains that contain organic carbon.

• Since carbon dating relies on the decay of carbon-14, it is important to note that this method is not used to date non-organic materials such as rocks and the earth's crust. These inorganic materials do not contain carbon-14, making them unsuitable for carbon dating.
• Observing that carbon dating is specifically versatile in estimating the time elapsed since an organism's death highlights its reliability in historical and prehistorical research.