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Real Life Applications

3 min read

- Wondering why to study this chapter? Know the real world use of it!

Radiocarbon Dating

Carbon forms the foundation for the life on Earth, starting from the microbes that appeared 3.7 billion years ago to humans that appeared around 2 million years ago. C-12 is constantly stored within the bodies of every biotic component of the biosphere through several life processes. Along with C-12, a radioactive isotope of carbon C-14 is found in every living organism in a ratio of one C-14 atom for every trillion C-12 atoms. Did you know, that even this trace amount of C-14 can help determining the archeological age of a fossil? Let us find out how.

C-14 is naturally produced in the atmosphere by the interaction of cosmic rays and atmospheric Nitrogen as shown in the reaction 1 above. C-14 radioisotope spontaneously decays using Beta decay pathway as shown in equation 2, and has a half life of 5730 years.

The ratio of abundance of C-12 to C-14 is given by :

\frac{n ( _{6}^{12} C )}{n ( _{6}^{14} C )} = 10^{12}

For all living beings, this ratio between the isotopes remains constant as the carbon within their bodies are constantly getting replenished because of life processes. However, after an organism dies the carbon accumulation stops and the C-14 count keeps reducing as time elapses.

By Radioactive Decay Law we can say,

N_{t} = N_{o} e^{- λ t}

Where

N_{t}

is number of active nuclei of C-14 in a sample,

N_{o}

is the amount of active nuclei when it was living and

λ

is the decay constant.

Half life of C-14 is

T_{1 / 2} = 5730 y e a r s

We can determine the decay constant using the half life equation,

λ = \frac{l n ( 2 )}{T _{1 / 2}} = 1.21 \times 10^{- 4} y e a r^{- 1}

Rearranging the decay law and using the value of the decay constant we can write

t = l n (\frac{N _{o}}{N _{t}}) . \frac{1}{λ} = 8267 l n (\frac{N _{o}}{N _{t}}) y e a r s

N_{o}

can be estimated by the natural ratio of C-14 in atmosphere and sample size.

Hence, we can determine the age t of a sample. Ideally, radiocarbon dating is accurate with fossils with an age of 40,000 years or above.

Your smoke detector could be radioactive!

Yes, Ionization based smoke detectors use Alpha radiation for smoke detection. However, the radiation is too small to cause any harm. Let us find out how ionization based smoke detectors are designed.

Ionization based smoke detector contain small amounts, around 2mg of artificial element called Americium(

_{95}^{241} A m

). Americium spontaneously decays into Neptunium using the alpha decay pathway. These alpha particles are captured within an ionization chamber inside the smoke detector circuit. Alpha particles are highly ionizing and ionize the oxygen and nitrogen atoms present inside the chamber and keep a steady current flowing in the detector circuit as long as it is switched on.

When smoke enters the detector, the smoke absorbs most of the alpha particles. This reduces ionization within the chamber and the current in the detector is cutoff triggering an alarm.

Radiation can cause cancer and can treat it as well!

Radiation is everywhere around us. While non ionizing radiations like radio waves and micro waves from commonly used devices are practically harmless, ionizing radiation like gamma rays, beta rays etc. originating from a radioactive nuclei can be potentially dangerous.

Ionizing radiation can penetrate inside the body tissues and ionize molecules as they move past them.

Ionizing radiation has enough energy to break bonds and directly damage tissues at the DNA level and in some cases indirectly ionize cellular water, creating radicals that damage tissues. Depending on the amount of radiation received, the tissues can be completely damaged leading to radiation burns or even organ failure.

In case of small exposure, the radiation might not fully damage cells but alter the DNA in such a way that may lead to uncontrolled growth of cells leading up to cancer.

Then how can radiation be used to treat cancer?

Modern radiation therapy delivers radiations to cancer tissues in such a way that the healthy tissues aren't affected. Once the radiation is delivered, cancer cells are rendered completely damaged and cannot propagate further.

The radiation delivery is extremely targeted in radiation therapy and in certain treatments, radioactive elements are linked with compounds that have an affinity towards the target area where cancer cells are present.

Let us learn about radiation therapy in a little more detail with this informative video.

What is cancer radiotherapy and how does it work? | Cancer Research UK

3 mins