Question

Radiocarbon is produced in the atmosphere as a result of
A. Collision between fast neutrons and nitrogen nuclei present in the atmosphere
B. Action of ultraviolet light from the sun on atmospheric oxygen
C. Action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere
D. Lightning discharge in atmosphere

Answer 1

Hint: The radiocarbon is the naturally occurring radioactive isotope of carbon. It is found in the earth surface, mainly present in the upper part of the atmospheric layer. The high energy cosmic rays from the sun constantly bombard with the particles in the upper atmosphere.

Complete step-by-step answer:
${}_{6}^{14}C$ is the naturally occurring radioactive isotope of carbon. It is formed in the atmosphere by the action of cosmic rays. The atoms of radiocarbon behave similarly like other isotopes of carbon except they weigh more and in an average of 5000 years they decay to nitrogen.
The nuclear reaction given below represents the formation of radiocarbon in the upper atmosphere as a result of the collision between fast neutrons and nitrogen nuclei present in the atmosphere
${}_{7}^{14}N+{}_{0}^{1}n\to {}_{6}^{14}C+{}_{1}^{1}p$
The high energy cosmic rays from the sun constantly bombard with the upper atmosphere. These high energy particles undergo a whole cascade of nuclear reactions resulting in slow-moving neutrons. These neutrons react with nitrogen atoms in the atmosphere and result in the formation of radiocarbon.
Therefore option A is the correct answer.

Additional information:
Radioactive carbon dating, it is a method to calculate the age of fossils by determining the presence of ${}_{6}^{14}C$. The radiocarbon ${}_{6}^{14}C$ formed in the upper atmosphere has too many neutrons the $\beta$-decays occurs to form ${}_{7}^{14}N$.
${}_{7}^{14}C\to {}_{6}^{14}N+{{\beta }^{-}}+\bar{\nu }$, where $\bar{\nu }$ is the antineutrino
It is used up by the plants and animals. When they die, the decay of ${}_{6}^{14}C$ will begin. By measuring the activity of ${}_{6}^{14}C$ in fossils and dead trees and comparing it with ${}_{6}^{14}C$ present in the atmospheric carbon, we can estimate the age of fossils.

Note: Understanding the nuclear reaction in the formation of ${}_{6}^{14}C$ will help to solve the problem correctly. The nuclear reaction showing the decay of ${}_{6}^{14}C$ is preceded by the $\beta$-decay. The age of fossils and dead trees are estimated by carbon dating method.