Question

What are pros and cons of radioactive dating ?

Answer 1

Hint: To solve this question we will first clear our concept of radioactive dating process, radioactive decay, half life of a substance and decay constant and then talk about what are the pros and cons of this measurement process. The use of radioactive dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural or man-made materials.

Complete answer:
Radioactive dating (often called radiometric dating) is a process for determining the age of any particle by measuring the amount of a given radioactive material it contains. Radioactive dating is a technique which is used to date materials such as rocks or carbon, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.

The probability of a parent atom decaying in a fixed period of time is always the same for all atoms of that type regardless of temperature, pressure, chemical conditions, or any other factors. This probability of decay is called the decay constant. The time required for one-half of any original number of parent atoms to decay is called the half-life.

Pros can be said as: The half life of radioactive substances can be empirically determined. The ratio of the parent atoms to the daughter atoms are often used to determine a precise age of that substance given the assumptions that none of the first parent atoms are eroded or lost during time calculation.

Cons can be said as: All radioactive dating except Carbon 14 are based on atoms found in igneous rocks. Fossils are almost not found in igneous rocks. So radioactive dating cannot be used directly to date fossils. The one exception can be Carbon 14. However Carbon 14 has a relatively short half life so it cannot be used on fossils much older than 50,000 years that makes it useful for anthropology but not geo history. Also the majority of fossils do not contain Carbon as they have been turned to stone.

Note: The mathematical expression that relates radioactive decay to geological time is \[D={{D}_{0}}+{{N}_{t}}({{e}^{\lambda t}}-1)\]. Here $t$ is age of the substance, $D$ is number of atoms of the daughter isotope in the substance, ${{D}_{0}}$ is number of atoms of the daughter isotope in the original composition of the substance, ${{N}_{t}}$ is number of atoms of the parent isotope at time t (the present), given by ${{N}_{t}}={{N}_{0}}{{e}^{(-\lambda t)}}$,
And $\lambda $ is the decay constant of the parent isotope, equal to the inverse of the radioactive half-life of the parent isotope times the natural logarithm of 2. The equation is most conveniently expressed in terms of the measured quantity ${{N}_{t}}$ rather than the constant initial value ${{N}_{0}}$.