Which of the following best defines radio waves?

Radio waves are indeed a type of electromagnetic radiation, characterized by their longer wavelengths within the electromagnetic spectrum. They range from about one millimeter to several kilometers in wavelength and have frequencies from 3 kHz to 300 GHz. This positioning within the electromagnetic spectrum places radio waves in the same family as visible light, infrared, ultraviolet, X-rays, and gamma rays, but at the lower energy end.

Radio waves are widely utilized in various technologies, including communication systems, broadcasting, and radar, due to their ability to travel long distances and penetrate through various obstacles, such as buildings and the atmosphere.

Other definitions mentioned do not accurately describe radio waves. Sound waves are mechanical waves that require a medium to travel, making them fundamentally different from electromagnetic waves. Particle radiation typically refers to high-energy particles, while gravitational waves are ripples in spacetime caused by massive accelerating objects, such as colliding black holes. All these are separate phenomena and do not share the defining characteristics of radio waves as electromagnetic radiation.