Electromagnetic radiation

Electromagnetic radiation includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. All of them are forms of energy carried by oscillating electric and magnetic fields.

No, electromagnetic radiation can travel through a vacuum. Sunlight reaches Earth across space, and visible light is one part of the electromagnetic spectrum.

In a vacuum, electromagnetic radiation travels at the speed of light, about 299,792,458 meters per second. In materials like glass or water, light travels more slowly.

X-rays have much higher photon energy than radio waves and can ionize atoms. That is why medical X-ray imaging uses controlled doses, while ordinary radio broadcasts are non-ionizing.