Final answer:
Gamma radiation is the emission of high-energy electromagnetic waves by a nucleus undergoing transition between energy levels. It has very short wavelengths and high penetration power, and unlike alpha or beta particles, it is purely electromagnetic.
Step-by-step explanation:
The type of radiation that occurs when the nucleus emits powerful energy in the form of electromagnetic waves is C) Gamma radiation. Gamma rays are very high-energy electromagnetic waves emitted from a nucleus following a transition between nuclear energy levels. In comparison to alpha rays, which consist of 2 protons and 2 neutrons, and beta rays, which involve the emission of electrons or positrons, gamma rays are purely electromagnetic and are much more penetrative, able to go through several centimeters of lead.
Gamma rays have the shortest wavelengths of electromagnetic radiation, no longer than 0.01 nanometer, and are significantly more energetic than X-rays. This makes gamma rays a form of ionizing radiation, which can be dangerous for living tissues as it may knock electrons out of atoms. Nevertheless, gamma radiation plays a crucial role in astronomical observations and the study of violent cosmic events.