Light is composed of tiny particles called photons, which are elementary particles of electromagnetic radiation. These photons have both particle-like and wave-like properties, known as wave-particle duality.
When light travels, it behaves primarily as a wave. It moves through space in the form of electromagnetic waves, which consist of oscillating electric and magnetic fields. These fields are mutually perpendicular to each other and also perpendicular to the direction in which the light wave is propagating.
The speed at which light travels through a vacuum is a fundamental constant of nature, denoted by "c," which is approximately 299,792,458 meters per second (or about 186,282 miles per second). This speed is extremely fast, and light can travel vast distances across the universe in relatively short amounts of time.
Light does not require any medium or material to propagate. Unlike mechanical waves, such as sound waves that require a medium like air or water to move through, electromagnetic waves like light can travel through a vacuum. This is because light is not a disturbance in a material medium but rather a self-propagating oscillation of electric and magnetic fields.
The mechanism by which light moves so quickly is explained by Maxwell's equations, which describe the behavior of electromagnetic waves. These equations, formulated by the physicist James Clerk Maxwell in the 19th century, show that changing electric fields induce magnetic fields, and changing magnetic fields induce electric fields. This interplay between electric and magnetic fields allows the wave to propagate through space without the need for a physical medium.
In summary, light consists of photons, which are particles of electromagnetic radiation. Light moves as electromagnetic waves, with oscillating electric and magnetic fields, and it travels at an incredibly high speed due to the fundamental properties of electromagnetic waves and their self-propagating nature.