Introduction Light and Colour History in the physics


How do we see colour? What enables visual perspective? Most people wonder how they experience different colour shades. The exploration of colour and light requires one to understand the concept of waves.

Waves have the high and low volts that make up a wavelength. “The length of the wave determines its energy for instance, a long wave has a low energy or frequency, while a short wave has high energy” (Riley, 138). The visible rainbow colours are therefore wavelengths of different magnitudes.

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The sun emits/radiates some waves within the visible wave-range and the human eye interprets this range as colours of the rainbow. According to Riley, the wavelength is the distance between the chests of one wave to the other and is denoted by the Greek symbol ‘Lambda’, ‘?’ (138). The colours are known as visible spectrum of colours namely red, orange, yellow, green, blue, indigo and violet. Therefore, the light’s wavelength gradually increases from violet to red.

Theory of Light and Colour

History in the physics lesson indicates that Isaac Newton was the inventor of light since 1672; he applied the logic of a prism to discover that the prism could split the sunlight to various colours often referred to as colours of the rainbow. This arrangement of colours was due to difference of the light wavelength (Shapiro, 287). The signature used to identify colour is therefore its wavelength, measured in nanometre (nm). Later, James Clerk Maxwell advanced Isaac Newton’s discovery by proving that light is a form of electromagnetic emission that contains waves of different magnitudes, mainly the visible light, the radio waves and the X-rays waves (Shapiro, 287).

Considering that light is an electromagnetic wave, then colour exists as part of this wavelength. Human sense of sight enables them to discover colour in the light wave. In line with Gurney, the violet colour has the shortest wavelength within the visible light while red has the longest (37). According to Gurney, the definition of visible light can therefore be “the range of wavelengths within the electromagnetic spectrum that the eye responds to” (37). However, the human eye fails to respond to the radiation of longer and shorter wavelengths than the visible light segments.

Measuring light wave

“The units for measuring the distance in a metric scale is nanometre abbreviated as nm, which is a very small scales since it is equivalent to one millionths of a meter (1 nm = 10-9 m)” (Gibson, 17). The resolution of one nanometre is therefore too minute for clear visibility in an optical microscope. The micron (µm) is equivalent to 1000 nm and therefore can be resolved on the microscope. Measuring the wavelength in microns makes it to become visible, but in comparison to other objects such as thickness of human hair or paper, the wave is very minute. These objects are hundreds microns bigger than the visible light wave (Gibson, 17).

Formation of colours

Light is an electromagnetic spectrum that is easily detectable through naked eye.

It is a mixture of various colours split into different lengths depending on their wavelength differences. According to Dixon and Smith, the human eye can see a wavelength of approximately 400-700 nm (9). The light wave is absorbed, transmitted or reflected. Any of these actions depend on the surfaces since the surface gives the wave its required colour range. If all the colours of the wavelength hit a surface and gets absorbed, then that surface is black, denoting that no light is reflected. The white light for instance the sunlight is a combination of various colours, and when it falls on an object, the object absorbs all wavelengths that interact with its molecules or electrons and reflects a certain wavelengths to the observer’s eye (Shapiro, 287).

In line with Shapiro, the dull object will absorb white light while the bright objects reflect (287). The colour of an object is therefore determined by the specific wavelength of light that the object absorbs. For instance, an object that absorbs the red wavelength of the white light and reflects all the other lengths is seen as green.

An object may appear red because it has absorbed the red colour and reflected all the remaining wavelengths, this is due to the reason that the two colours complement each other in a similar manner as the orange does to blue or yellow to violet. Contrary, the transparent objects transmit white light. The diagram below illustrates the reflection light on a blue surface.

Measure of wavelengths

Different wavelengths are compared to a standard measure known as the electromagnetic spectrum. “The infrared and radio waves are often on the extensive wavelengths, thus on the long side of the electromagnetic spectrum, while the wavelength of the x-rays, gamma rays, and ultraviolet (UV) light are short wavelengths thus falling on the short side” Dixon and Smith (30). According to Dixon and Smith, the wavelengths with shorter than 400nm are not visible to the naked human eye (30). Human beings can therefore not sense wavelengths of measures greater than seven hundred nm. The white light is made of various protons that differ depending on the colour they represent due to energy differences.

These protons create various pulsating turbulence on the wavelength, which determines the colour of an object ranging from red to violet. The diagram below illustrates the light wave spectrum.

Perception of Colour

The definition of colour is consequently the spectrum of energy that enters the human eyes.

Human eyes have cells called rods and cones on the retina that absorb light and assist in distinguishing between various colours (Dixon and Smith, 30). The rods assist in diffusing light and therefore support in sensing differences of reflections and in determining differences in light intensity. In dim lighting people perceive coloured objects as grey shades, therefore the retina has three sets of cones, which are all good receptors of light. The colour of an object depends on the light wave sent to the eye from all the possible variations of colours in the sunlight. Every human being sees different variations of colours, thus different shades due to uniqueness of the cells, mainly the rods and cones. The colour pigments are different from light waves since they are made of various colours.

Pigments are made of mainly three primary colours; red, blue and yellow, three secondary colours; violet, orange and green and six tertiary colours made by mixing a primary and a secondary colour. The pigments are materials that either let colours to pass through or absorb them (Gurney, 38). On the other hand, the primary light colours are blue, red and green and secondary light colours are magenta, cyan and yellow. Mixing of light colours causes formation of an additive that eventually leads to formation of white light. The splitting of light can also be addressed as a subtractive procedure since some of the light wavelengths are absorbed and the only visible wavelengths are those that are carefully given off during the process. The three colour codes of the white light enhance perception of other colours (Gurney, 38).

The colour

Colour is made of three main factors namely hue, luminance and saturation.

Type of colour depends on these three factors for instance, hue is the shade of a colour and saturation is the pureness of the hue. Luminance is the description given when defining a colour as either light or dark. People who have difficulties of perceiving the red and green pigments suffer from a problem associable to colour blindness since they lack the red and green colour pigments. According to Gurney, the difficulties of making out the green to red ratio are a defect mainly associable to X-chromosomes and therefore affect men more than women (139).


Some colours have negative effects for instance those on a bright light waves that reflect more light. They may cause eye irritation or cause headaches for instance the bright yellows on surfaces or on computer washouts. The bright colours are thus able to reflect more light waves into the eye and cause irritation or straining.

The bright colours are thus used to attract people attention for instance on posters of road signs. Colours also influence moods, for instance the blue colour can rein in the appetite for food since food do not naturally exist in blue. There are colours that comfort the sense of sight for instance green, which is known to sooth and comfort. The colour may therefore be perfect for a work scenario to curb possible work-related signs of fatigue.

Works Cited

Dixon, Malcolm. and Smith Karen. Light and colour: Young Scientists Investigate Series.

London, UK: Evans Brothers, 2005. Print. Gibson, Gary. Light and Colour: Fun Science Projects Series. Franklin Watts Books. 2009. Print. Gurney, James.

Colour and Light: A Guide for the Realist Painter. Missouri, MO: Andrews McMeel Publishing, 2010. Print. Riley, Peter. Light and Colour: Making Sense of Science Series. Franklin Watts Books.

2008. Print. Shapiro, Alan E. Fits, Passions and Paroxysms: Physics, Method and Chemistry and Newton’s Theories of Coloured Bodies and Fits of Easy Reflection. Cambridge, UK: Cambridge University Press. 2009.



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