Understanding Light and Photochemistry

Light is a rudimentary constant in life; it is easy to consider it as something that’s simply there. But to understand how light can affect biology, it is important to first understand the basic physics of how light works.

Light is energy. In most cases, it is emitted as a result of a thermal reaction, such as the sun’s nuclear fusion or the hot filament in an incandescent bulb. Though it may seem constant and connected, like a string connecting one thing to another, light is actually made up of packets of energy, called photons that have the physical properties of both wave and particles.

These particles, like all forms of electromagnetic radiation (i.e., X-rays or AM/FM Radio) travel closely to each other throughout the universe in a wave pattern. When the waves of light energy are far apart, it is said to be infrared light. When the waves are close together, it is ultraviolet. And in between those two ranges is visible light, when the waves are moving at just the right frequency that they can be seen.

Light Interacts With Matter

Even though light is seen as passive or ambient energy, its particle composition means it can interact with physical matter like atoms, molecules, or cells. It is even possible for light to exhibit pressure; it can move things, albeit only very small things.

Photochemistry is the study of how light energy triggers chemical reactions when it is absorbed by matter. The most commonly recognized photochemical reaction is photosynthesis, where plants create sugars from the reaction of light energy and carbon dioxide. 

In human biology, vitamin D is created as a reaction when the skin absorbs light from the sun. And key to light therapy, light can be absorbed by cells.


This website is intended for healthcare professionals and clinical researchers only. All of the treatments using LED phototherapy devices that are discussed on this website are in various stages of investigation and have not been approved by the FDA except where specifically stated.

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