Question

Gamma rays are among the highest energy electromagnetic radiation because:

• A. Gamma rays are emitted due to alpha decay.
• B. They are emitted from radioactive elements.
• C. They are the consequence of nuclear energy transitions and nuclei have very high difference between the allowed energy states, of the order of few MeVs.
• D. All of the above.

Answer 1

The correct option is C They are the consequence of nuclear energy transitions and nuclei have very high difference between the allowed energy states, of the order of few MeVs.

As you know well now, my young Padawan, like the electrons, the nucleons also exist in various energy states. Now, as these energy states are predominantly because of strong nuclear force, in contrast to Coulomb force for electrons, they are very large! (As the strong force is orders of magnitude stronger than the Coulomb force), and so are the difference between the energy states (of the order of few MeVs). Hence the usual methods of heating etc. cannot excite a nucleus.
Now, gamma rays are emitted when a nucleus transitions from higher energy state to ground state. The energy the nucleus loses in the process is very high, and hence, the energy of the gamma rays emitted is very high.