Light is all around us, from a basic lightbulb to humans like you and me. But to understand light and its roles in the universe scientifically we must think of it as radiation. The electromagnetic spectrum is all the energy the universe can emit through radiation and radiation is transmitted through photons which can be casually described as massless little packets of energy. There is light we can see, known as visible light, but there is also light we can’t see: Infrared, Radiowaves, Micro, Gamma rays, X – Rays.

All types of light – henceforth known as radiation – is produced in one of  two ways:

1. The kinetic energy of particles
2. Matter

Electromagnetic radiation can be produced through the kinetic energy of particles, through a process called blackbody radiation. When a particle has kinetic energy it produces thermal energy. This thermal energy comes from the kinetic energy of a particle either vibrating, translating, or rotating – the distinction between the three has to do with the type of matter the particle is in. Particles in solids tend to vibrate or rotate, while liquid or gas translate more freely. The thermal energy in these systems are converted to blackbody radiation, as anything with thermal energy emits radiation.

Electromagnetic radiation can also be generated through interactions with matter. An electron has different energy levels and when it goes to a lower energy level the product is a photon. Conversely, when it jumps to a higher energy level it absorbs a photon. A lower energy level leads the electron to move a shell closer to the nucleus, and a higher lea it a shell away. This phenomena is called a quantum leap. 

Energy of a photon

hC/λ

h = Plancks constant 

C = speed of light (3.00 x 10⁸ m/s²)

λ = frequency of wave

This equation shows that the energy of light is inversely proportional to its wavelength. Shorter wavelengths, like gamma rays, carry more energy, while longer wavelengths, like radio waves, carry less. One of the most fascinating discoveries in physics is that electromagnetic waves, like gravity, are a property of spacetime itself. A changing electric field generates a magnetic field, and vice versa, leading to the propagation of electromagnetic waves through spacetime. Unlike sound, which requires a medium like air to travel, electromagnetic waves do not need a medium and can move through the vacuum of space at a constant speed. They are a fundamental feature of the universe, woven into the very fabric of spacetime. This article establishes a foundational understanding of light and is highly recommended to read before reading upcoming articles.