Section 6.2 Electromagnetic Waves Electromagnetic radiation is an important wave type that includes gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, and radio waves. All types of electromagnetic radiation travel at the same wave speed, which for historical reasons is referred to as the speed of light . Visible light and the other types of electromagnetic radiation do not need a physical medium for their propagation. They can travel through a vacuum, although they can also travel through transparent media such as glass and water. Sunlight comes to us on Earth through essentially empty space, but it also penetrates through the gases of our atmosphere and can be detected at great depths in our lakes and oceans.
Light is a transverse wave.
When a light wave passes a given point, changes occur in the electric and magnetic properties of space perpendicular to the direction in which the wave is traveling. That is why light is classified as a transverse wave even though no physical material is involved in the oscillations that occur. It is the variations in the electric and magnetic character of space that are responsible for the transfer of energy in all types of electromagnetic waves. The frequency and wavelength for electromagnetic waves vary widely from one type to another, and every type has its own range of values for each of these properties. That is how we distinguish one type of electromagnetic radiation from another.