Which term describes the radiation that includes visible light and X-rays, characterized by varying electric and magnetic fields?

The correct choice identifies electromagnetic radiation, which encompasses a range of radiation types, including both visible light and X-rays. These forms of radiation are characterized by the presence of oscillating electric and magnetic fields that propagate through space.

Electromagnetic radiation spans a broad spectrum, from low-energy radio waves to high-energy gamma rays, with visible light falling in the middle of this spectrum. The electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of wave propagation, which is a defining characteristic of electromagnetic waves.

This understanding of electromagnetic radiation is vital as it demonstrates how different types of radiation can have diverse applications and effects. For example, visible light enables us to see, while X-rays are utilized in medical imaging due to their ability to penetrate through soft tissues and reveal structures like bones.

The other terms mentioned refer to different phenomena; sound waves relate specifically to mechanical vibrations in a medium, while particle radiation involves the emission of particles such as alpha and beta particles. Thermal radiation is associated with the emission of energy in the form of heat due to an object's temperature. Thus, the term that accurately encompasses both visible light and X-rays, along with the nature of their interaction with electric and magnetic fields, is electromagnetic radiation.