White, Light, Optics

Today I’ve started my day reflecting on the deeper and symbolic meaning that colors may have. For example in ancient Egypt the men related to religion and god adoration was used to dress only in white linen. Perhaps the first analogy that you may have now in mind is how some people are used to the same habit when they want to underline their suntan during the time of a sea or island vacation, right?

White is the first main color chosen by brides for their wedding cause it represent purity and a union of the pure of heart and from a scientific glance. First of all I must say that white is the color of the natural illumination of our Sun and the one of the brightest extended surface able to reflect its rays on us during winter time. The peaceful mountain or higher places with abundant and long lasting snowfalls are a reference for this claim.

Sunlight is made of beams and when one of them passes through a prism the spectrum of colors emerges and a similar effect, such as the one that happen when water droplets in the air, maybe after a temporary storm, pass through sunlight to create a beautiful rainbow. It was Newton’s proposal that withe light (including the one that come from the Sun) is a mixture of many basic different colors that were present beforehand.

Newton’s way to test his inferences was a simple but efficient experiment, when the spectral colors (including white light analyzed by a prism) can be reassembled again from it when passing through a second prism. As with the latter it is possible to reverse the separation and get back to white light taken as first element to start with.

Each spectral color is a purified section of light, containing only photons of one kind so to identify clearly the elements that compose it. Why am I saying that for? Well, if you are curious enough you can realize a periodic table of light by yourself using a beam of sunlight or the light produced by a glowing hot body through your prism and by projecting your output to a screen you will made your reliable periodic table safely.

If you decide to use only part of the spectrum the combined light will be no rather only white, but a sort of combination for colors that can come through. Sometimes you can see, using natural light as original source, the blue end of the spectrum lopping off or maybe the green dominance above the perceived color, such as the case when red take the scene when a narrow band of them is letting through.


Interpret this experiment could be easy if you assume that sunlight consists of photon that can come in different sorts, with different shapes or different masses that are affected by the prism’s glass in different ways.  The prism separates them by bending atom’s trajectories and letting our eyes produce the sensation of different colors.

If we are curious enough to reproduce this effect at home we’ll see how a small portion of light’s spectrum can let us obtain beams of pure spectral color. Their components will be defined by the same percentage of bent passing through the prism at disposal.

Trying to find an answer to the doubt of any possible further processing, revealing additional structure or purification he subjected his purified beams (the ones of spectral colors) to different empirical settings reflecting them through lenses and prisms of partially transparent surfaces, avoiding common glass, to found that this process reflect what was performed by his first prism.

During the reflection we can note that spectral green remains the same, as well as the spectral blue. Another effect that happens very commonly is that this light can be absorbed by objects in the closest area, for example an object that we see blue can absorb all the spectral colors except for those close to blue, which it reflects and that’s the reason why it appears blue.

I’m sure that you are familiar with the word ‘refraction’, right?

It happens when a given material refract the rays of light (of a given spectral color) in a definite way cause they retain their integrity.  Thanks to this phenomena, Newton arrived to prove that light beams are pure substances defined by fixed and reproducible properties. The detail to be noticed is that white does not appear in the spectrum, mainly cause it can be analyzed into component spectral color appearing as a mixture.

Going back to the initial symbolism associated to white, if we talking about light of course, its features are never pure. But let underline how the analogy with ‘white’ and ‘light’ was an important and fruitful source of scientific discovery and maintain even nowadays a strong, deep, transforming touch of poetry.







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