By: Bernadine Rodrigo
As most of us learn in school and some found it more difficult to understand than others, colour comes from light. If not for light, there would be no colour. If not for colour, there would be no light. “Light is what we see”, some may say. However, as we go up the years in school, we learn that while light touches everything we see, we do not see all light. Light comes in a spectrum, which we call the electromagnetic spectrum. In this spectrum we find that this light that we see is an extremely minimal amount when compared to the light that we do not see. Indeed, it is extremely ironic to hear the phrase: “Light which we do not see”, but alas! Such is the way of life. This light, or rather this spectrum, which consists of such a deep, poetic aura is not simply some tangible object which floats around the earth in an orderly manner with the visible section hitting each person with the capacity to see, individually.
University of Colombo physicist Dr. Jayasekara* breaks down what the substance or matter of light really is. He goes back to the late 1600s, when the great Sir Isaac Newton – whom Dr. Jayasekara refers to as someone who “discovered something about everything” – conducted research based on the “corpuscular” nature of light which describes light as tiny particles. Sir Isaac went on to show that light does have particle-like qualities. Then in the 1800s a Dutch physicist Christiaan Huygens began to describe light as not particles but rather, having a wave-like form in nature. Following this revelation, another physicist at the time, James Clark Maxwell developed the theory of light being “electromagnetic” and displayed that light is energy emitted from both electric and magnetic fields. Therefore, when light travels around, we say that it is being radiated.
Later, as Dr. Jayasekara narrated, Einstein in the 1900s published his “photoelectric” theories where he displayed that light was in fact particles. “Afterwards, people really began to know what light was,” Dr. Jayasekara said. Scientists started conducting experiments based on the ‘quantum theories’- tiny particles which ultimately revealed the facts about the small particles of light known as photons and also showed that light not only comes in particles, but also in waves. “It depends on the method in how light is measured,” resolved Dr. Jayasekara, “If you measure it one way, it will show wave-like properties and if you measure it another way, it shows particle-like properties.”
Once again, it can leave one in wonder that we look directly into this energy every day, when we often think of energy as a non-perceivable thing which simply travels around us performing magical acts such as creating the essence of life.
This fascinating visible bit of energy is indeed a little part of the spectrum, and the reason we can see this little part is that the light in that specific part of the spectrum consists of the perfect “wavelength”, which can be perceived by the human eye, according to Dr. Jayasekara. The wavelength is the space between two adjacent crests – the topmost points in a wave of light. We humans are only capable of seeing light, that is, colours, which have wavelengths between 380-700 nanometres. We must notice that nanometres are 1/1,000,000,000 of a metre.
The colours of that region are known as visible light and primarily consist of what we aesthetic humans refer to as the “colours of the rainbow”. It starts with violet, at the shortest wavelength and then goes on to indigo, blue, yellow, green, and orange, up to red, which consists of the highest wavelength. Those with shorter wavelengths – below violet, beginning from ultra violet – and longer wavelengths – above red, beginning from infra-red – cannot be seen by the human eye.
The human eye perceives light once again not in a very simple process but, through one which requires more effort than what it takes to lift a finger. Yet, we do it every day, the same way in which we breathe; involuntarily and unknowingly. This develops as one grows, especially during a time scientists refer to as the “critical window of growth”. This is the toddler or very young age of the human life cycle when the neurons of the body adapt to all stimuli. Through experiments done with animals such as kittens, it has been found that during these years, if the proper stimulus is not received, then this skill of vision may never develop.
As the natural science of physics is used to explain the existence of light, how we see can be explained through the use of the science of biology. This process is far too complex and indeed may be a slight bit too tedious for someone who is simply interested in learning about colour to read about.
Colour too, however, is as twisted as the process of receiving this vision. It may be believed that most of us are quite aware that the light we see as a colour of a certain object is not in fact the true colour of that object, but is simply the colour which is reflected by the surface of the object. Therefore, if we are prone to jumping to conclusions, we can assume that it is the sun that reflects light in the colour yellow. Then, we may find ourselves confused because we may recall that the sun emits white light which consists of all seven colours.
Then, what is yellow light and why do we always use yellow paint when making an artwork of the sun?
Yellow is a colour – a wave or ray – which is somewhere in the middle of the visible light spectrum. It is about 577-597 nanometres, which is comfortably visible by the human eye. “I don’t know when to call it yellow,” said Dr. Jayasekara, “Yellow is a very diverse colour. It takes up a large space on the spectrum and also melts into other colours adjacent to it.”
We may not have often noticed however that yellow is an awfully abundant colour and is certainly eye-catching. Most often, when one is a child, yellow seems not to be the most appealing of colours, however, as one grows older, it is possible that yellow is somewhat of a relaxing and even joyous colour. Perhaps colours with higher wavelengths such as yellow do have an element of joy in them as year after year when ‘tis the season to be jolly, red – another colour with a large wavelength – is to be seen in almost every single location.
Yellow however, is closer to countries in the tropics such as Sri Lanka. Yellow can often spark a feeling of relaxation and calmness, reminding folks of the sunny beaches and warm golden sands. Yellow blends in. Yellow stands out.
How then, do we see the sun in this colour? In truth, the sun does emit white light – white light containing not simply the visible light within it, but also the rest of the waves of energy present in the spectrum. The reason for our perception of yellow in the sun lies in the atmosphere of our planet. Consisting of multiple layers and various gases, the earth’s atmosphere is built so that it may shield the surface from harmful radiation from the sun. Therefore, rather altruistically, the atmosphere absorbs and scatters away the waves with smaller wavelengths and only allows the colours with larger or more comfortable wavelengths to reach our eyes, said Dr. Jayasekara. This phenomenon is studied in the field of “quantum electrodynamics” introduced largely by the famous American physicist, Professor Richard Feynman. This field elaborates how light interacts with matter.
However, although yellow may be a comfortable colour and despite the earth’s atmosphere believing so, we must stick to not looking directly at the sun as it is far too great a stimulus for the eye to cope, with the way it does daily things.
Finally, we can reach the conclusion that light most certainly is not what meets the eye.
*the name of the expert has been altered in order to protect his identity as per his request