Electromagnetic wave

Light from the Sun reaches Earth through the vacuum of space. It is an electromagnetic wave: a travelling oscillation in electric and magnetic fields. Unlike sound, it does not need matter to carry it.

Visible light is only one kind of electromagnetic wave. Radio waves, microwaves, infrared, ultraviolet, X-rays and gamma rays are electromagnetic waves too. Although these names identify different parts of the electromagnetic spectrum, every member of the family has the two properties considered here: it is transverse and it travels at the same speed in a vacuum.

In an electromagnetic wave, the electric and magnetic fields oscillate at right angles to the direction of travel. EM waves are therefore transverse.

Light is an electromagnetic wave. Unlike a mechanical wave, it does not require particles of a material to pass on a disturbance, so it can travel through a vacuum as well as through substances.