Section-C: Comprehension Type
Various rules of thumbs have been proposed by the scientific community to explain the mode of radioactive decay by various radioisotopes. One of the major rules is called the n/p ratio. If all the known isotopes of the elements are plotted on a graph of number of neutrons (n) versus number of protons (p), it is observed that all isotopes lying outside of a “stable” n/p ratio region are radioactive as shown in figure.
The graph exhibits straight line behavior with unit slope up to p = 25. Above p = 25, those isotopes with an n/p ratio lying below the stable region usually undergo electron capture while those with n/p ratios lying above the stable region usually undergo beta decay. Very heavy isotopes (p > 83) are unstable because of their relatively large nuclei and they undergo alpha decay. Gamma ray emission does not involve the release of a particle. It represents a change in an atom from a higher energy level to a lower energy level.
Which of the following represents the relative penetrating power of the three types of radioactive emission in decreasing order?