The Science Behind Visible Light and Color Perception

Understanding the science behind visible light and color perception is crucial for anyone working in fields such as graphic design, photography, or even simply curious about the workings of our world. This article aims to clarify the commonly perceived rainbow colors and delve deeper into why we see certain wavelengths and not others.

Newton's Rainbow and Modern Color Schemes

Traditionally, we think of the rainbow as consisting of seven colors: red, orange, yellow, green, blue, indigo, and violet. However, this classification was introduced by Sir Isaac Newton in the early 18th century. Interestingly, when Newton used the term 'blue,' he was likely referring to what we would now call cyan. Similarly, the term 'indigo' was often used to denote a specific shade of blue. Today, we recognize a more precise color scheme within the visible spectrum:

The reason for the difference lies in context and advancements in our understanding of optics. Contemporary knowledge helps us appreciate the nuances in color perception and categorization.

Why Do We See Some Colors and Not Others?

The human eye is particularly sensitive to certain wavelengths of light within the electromagnetic spectrum. We don't simply choose to see certain colors; rather, it is a biological and physiological reality based on the sensitivity of our visual systems.

Each light wavelength corresponds to a specific color. If our visual systems were tuned to a different range, such as the infrared or ultraviolet spectrum, we would perceive different colors. Wavelengths outside our visible spectrum would be invisible to us, just as radiation at 450nm would be invisible if our visual systems were sensitive to a different range.

Reflecting and Absorbing Light

Objects appear to have specific colors because they reflect some wavelengths and absorb others. The light we see is the light that is reflected or transmitted by the object. When all visible light is absorbed, we perceive it as black. Conversely, when all visible light is reflected, we perceive it as white.

Color Perception in the Human Eye

Our eyes contain three types of photoreceptors: cones. These cones enable us to perceive different colors. The range of light wavelengths we can detect is approximately 4500 angstroms to 7000 angstroms, corresponding to violet and red light, respectively. The phenomenon where all colors converge to white in Newton's disk experiment is a physical demonstration of this principle.

White light does not contain all colors as a composite; rather, it is a combination of different colors that stimulates our red, green, and blue cones equally. Interestingly, some color blindness conditions can be traced back to shifts in the response curves of these receptors, often leading to the activation of one receptor that almost duplicates the response of another.

Conclusion

Understanding the intricacies of visible light and color perception is not only fascinating but also crucial for fields that rely on precise color matching and representation. Newton's original color order was a significant step in scientific understanding, but modern knowledge provides a more accurate picture. By delving into the science of light and color, we can better appreciate the complexity and beauty of our visual world.