Although there are many forms of waves in the electromagnetic spectrum – like x-rays, radio waves, microwaves etc. - light is the only form of electromagnetic radiation that is visible to the human eye.
Light is produced by various sources including the sun, light bulbs and electronic displays and plays a fundamental role in our perception of the world around us.
Our eyes do not differentiate between individual wavelengths, but rather have receptors that react to red, green, and blue light.
Light can behave like a wave with properties such as wavelength, frequency, and amplitude, or like a particle with properties like energy and momentum.
Light is characterized by its wavelength, which refers to the successive crests and troughs of a wave of light.
The wavelength of light visible to humans ranges from short at about 400 nanometers (nm) for violet light to long at about 700 nm for red light.
See how different wavelengths correspond to various perceived colors.
Light is the stimulus for color perception. We can perceive the color of an object through the reflection of light.
When light hits an object, some of the light is absorbed while some is reflected.
When we see a red apple, for example, the apple is reflecting more long wavelengths than middle or short wavelengths. Our eyes send a signal to our brain that interprets the distribution of wavelengths from the visible spectrum and leads to our perception of red.
Since we are seeing red light reflected from the apple, the light source itself must contain red wavelength light. Without any red light wavelengths in the light source, the apple would not look red.
There are 3 elements required for color perception: a light source, an object, and an observer.
Similar to the adage, “If a tree falls in the forest and no one is there to hear it, does it make a sound?” …If light hits an object but no one is there to observer it, is there a color?
Color can be created by combining or removing light.
Additive and subtractive color mixing are two different ways of combining colors to create new ones.
Additive color mixing is used when working with light. If different colored lights are combined, they create a new color.
For example, when red, green, and blue lights are mixed in equal amounts, they create white light. Adding fewer colors or reducing the intensity of the combined colors will result in different shades and hues. This is how computer monitors, televisions and other electronic displays create color.
Subtractive color mixing is used when working with pigments, inks, or dyes. If different pigments are mixed, they subtract wavelengths of light, and the result is a new color that is a combination of the remaining wavelengths.
For example, when cyan, magenta, and yellow pigments are mixed in equal amounts, they create black. Adding fewer colors or reducing the amount of combined colors will result in different shades and hues. This is how printers create color.
Additive color mixing involves adding light to create new colors.
Subtractive color mixing involves subtracting light by using pigments or dyes.
We see colors through a complex process that involves our eyes, brain, and the surrounding environment. When light enters our eyes, it is focused by the lens onto a layer of light sensitive cells at the back of the eye called the retina.
Our retinas contain two types of cells that are responsible for color vision: rods and cones.
There are 3 types of cones and each one is sensitive to a different range of wavelengths of light: short wavelengths (blue), medium wavelengths (green) and long wavelengths (red).
When light enters the eye and strikes these cones, they send electrical signals to the brain through the optic nerve, then the brain processes these signals in different ways to create the perception of different colors.
For example, when the signals from the red and green cones are combined, the brain perceives yellow. Similarly, when the signals from all three types of cones are combined, the brain perceives white.