How light is electromagnetic in nature?

Light is electromagnetic in nature because it is composed of fluctuating electric and magnetic fields that propagate through space as transverse waves, carrying energy from one point to another without the need for a medium.

To understand the electromagnetic nature of light, we must first look at the work of the Scottish physicist James Clerk Maxwell in the 19th century. Prior to his work, electricity and magnetism were considered separate forces. Maxwell's groundbreaking set of four equations, now known as Maxwell's Equations, unified these two forces into a single, comprehensive theory of electromagnetism. 

His equations predicted that a changing electric field would create a magnetic field, and a changing magnetic field would, in turn, create an electric field. This elegant, self-perpetuating cycle of oscillating fields would then travel through space as a wave. Maxwell calculated the speed of this hypothetical electromagnetic wave and found it to be incredibly close to the experimentally measured speed of light. 

This led him to the astonishing conclusion that light itself must be an electromagnetic wave. This was a monumental discovery that laid the foundation for modern physics.

So, what does this actually mean? It means that light is not a simple particle or a mechanical wave that needs a medium to travel, like sound waves. Instead, it is a transverse wave, which means the oscillations of the electric and magnetic fields are perpendicular to the direction of the wave's travel. Imagine a ripple on a pond; the water moves up and down (transverse) while the ripple moves forward. 

Similarly, in an electromagnetic wave, the electric and magnetic fields oscillate at right angles to each other and to the direction of propagation. The entire collection of these waves, from low-frequency radio waves to high-frequency gamma rays, is known as the electromagnetic spectrum. Visible light is just a tiny sliver of this vast spectrum. All these waves, including light, travel at the same speed in a vacuum—the speed of light (c), which is approximately $3 \times 10^8$ meters per second. 

This speed is a fundamental constant of the universe. The different types of electromagnetic waves, such as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, are distinguished from each other by their frequency and wavelength. The wave nature of light explains phenomena like diffraction (the bending of light around obstacles) and interference (the constructive and destructive combination of waves). 

While the wave model is essential, it's also important to note that light has a dual nature—it can also behave as a particle, a concept known as the photon, which explains phenomena like the photoelectric effect. This wave-particle duality is a cornerstone of quantum mechanics, but the fundamental understanding of light's electromagnetic nature remains the foundation for almost all of our modern technology, from telecommunications to medical imaging.