Colour theory in Phyisics
INTRODUCTION
In 1666, Sir Isaac Newton unravelled the secrets of colour by slicing white light into a rainbow using a glass prism. This experiment demonstrated that white light is not singular but composed of multiple wavelengths. Today, using Three.js, we can simulate this same phenomenon, breaking apart light to reveal the hidden spectrum.
CHAPTER 01
Let's take a beam of red light. Now add a beam of green. And finally, a beam of blue. Let's combine them what do you think happens? Unlike paint, which blends subtractively, light follows the rules of additive colour mixing. The three fundamental colours of light—red, green, and blue (RGB)—form the basis of everything we perceive in the visible spectrum. These are the primary colours of light because they cannot be created by mixing other colours; rather, they combine in varying intensities to generate every colour we see.
If you isolate a beam of red light, it remains red, just as green and blue do when separate. However, when these beams overlap, something remarkable happens: they interact additively. The more light you add, the brighter it becomes. This is why when red, green, and blue converge fully, they create white light.
This is the same principle used in digital screens, projectors, and even how the Sun emits visible light across the spectrum. But what happens when we don’t fully combine these colours? What new hues emerge?
Yes, white light is not the absence of colour—it is the presence of all colours. This is the very nature of additive colour mixing. But why does this happen? Why does light behave so differently from the pigments we paint with?
CHAPTER 02
Now that we understand red, green, and blue as the foundation of light, let’s explore what happens when they are mixed in different proportions.
These new colours—cyan, magenta, and yellow—are known as secondary colours of light. Unlike the pigments we mix in paint, light blending adds wavelengths together rather than subtracting them. This is why digital screens work in RGB and why stage lighting can create stunning effects with just three primary light sources. By controlling the intensity of each light source, an infinite range of hues can be generated. This is the principle behind all modern display technologies.
CHAPTER 03
Every colour of light has a specific wavelength, measured in nanometres (nm). The human eye perceives only a narrow band of electromagnetic radiation—the visible spectrum—which ranges from approximately 380 nm (violet) to 700 nm (red).
This is why blue light appears more energetic, while red light feels warmer and more soothing. Interestingly, some animals can see beyond human perception—bees detect ultraviolet light, and snakes perceive infrared. This opens up an entirely different view of the world, one shaped by invisible colours that lie just beyond our reach.
WAVELENGTH
CHAPTER 04
Building upon his earlier discoveries, Sir Isaac Newton introduced the first colour wheel in 1666. This concept can be deconstructed into distinct categories: primary, secondary, and tertiary. Primary colours—red, green, and blue—are the building blocks of all others, while secondary and tertiary colours emerge from their combinations.
Carl Jung proposed that colour is deeply connected to the human psyche, influencing emotions, thoughts, and even subconscious patterns. According to Jung, colour plays a role in personal development, symbolism, and archetypes. Red represents passion, vitality, and primal energy, but also danger and aggression. Blue symbolises calm, intellect, and spirituality, evoking a sense of stability and introspection. Green is linked to balance, healing, and nature, reflecting growth and harmony. Yellow signifies creativity, enlightenment, and optimism, but can also indicate caution. Black & White represent the duality of existence—conscious and unconscious, known and unknown.
Jungian colour theory suggests that different hues resonate with our inner selves, shaping how we perceive the world and how we interact with it. In this chapter, we explore how these psychological aspects intersect with physics, bridging the material and the metaphysical.
CHAPTER 05
Now let’s introduce another variable; motion. What happens when coloured light moves? The answer lies in the Doppler Effect. Consider this: If an object emitting light is moving toward you, its waves compress, shifting toward the blue end of the spectrum. If it moves away, the waves stretch, shifting toward the red. This phenomenon, known as redshift, is crucial in astronomy. It allows astronomers to measure the expansion of the universe, as distant galaxies appear redshifted as they move away from us, revealing the dynamic nature of the cosmos.
Astronomers use this principle to determine whether a star or galaxy is moving toward or away from us. A blueshift indicates motion toward us, while redshift means the object is receding. Most objects in the universe exhibit redshift, supporting the Big Bang theory, which suggests that the universe is expanding continuously, as predicted by cosmic inflation and particle physics models.
A practical way to understand the Doppler Effect is through sound. Imagine a car passing you at high speed: as it approaches, the pitch of the engine is high, but as it moves away, the pitch drops. This shift in frequency is the same principle that applies to light waves. It’s also why the setting sun appears red—its light has to travel through more of Earth’s atmosphere, scattering away the shorter blue wavelengths and leaving behind the deeper reds.
CONclusion
Now, imagine a world where you could see beyond the visible. Where ultraviolet and infrared weren’t just scientific concepts, but part of your everyday reality. Some animals, like bees and snakes, already perceive these hidden wavelengths—detecting patterns and heat signatures invisible to us. What would our world look like if we could do the same? Would the sky still be blue? Would a rainbow still appear as it does now? Or would everything around us transform into something unfamiliar?
Perhaps the real question is this: Is colour an inherent property of the universe, or merely an interpretation shaped by our minds? As we manipulate light, shift wavelengths, and play with perception, we begin to see that colour is not absolute. It is dynamic, fluid—changing based on context, observation, and the limits of our biological senses. The colours we experience are not fixed truths but interpretations, constructed by our brains to make sense of an otherwise invisible spectrum.
So, if everything we see is a construct of perception, then what is reality? What lies beyond the boundaries of vision, waiting to be revealed? Perhaps, in the grand expanse of the cosmos, the most extraordinary colour of all is the one we have yet to perceive.