The visual experience of colour is associated with words such as red, yellow and blue.
Things appear coloured to an observer because colour relates to properties of light that are visible to the human eye.
Properties of light that produce the experience of colour include wavelength, frequency and energy.
- We see colour as a result of:
- The range and intensities of wavelengths of visible light emitted by a light source.
- The path that light takes and the different media and materials it encounters on the journey from its source to the retina of a human eye.
- Optical phenomena such as absorption, dispersion, diffraction, polarization, reflection, refraction, scattering and transmission.
- An observer’s predispositions, including their personal and social experience and cultural context.
About light and colour
- Light is electromagnetic radiation (radiant energy), which is transported by electromagnetic waves (or their quanta, photons) and travels through space.
- Even if humans had never evolved, electromagnetic radiation would have been emitted by stars since the formation of the first galaxies over 13 billion years ago.
- Colour perception in humans primarily depends on the design of our eyes and the wavelength, frequency, and energy of the visible light that strikes the retina at the back of our eyes.
- Colour is a visual experience unique to each of us at any given moment because of our different points of view and perspectives on the world. So we share our experiences of colour using language to share our experiences of colour.
About white light
- White light is the term for light that contains all wavelengths of the visible spectrum at the same intensity.
- The term ‘white light’ doesn’t imply that light appears white while travelling through the air. As light travels through the air it is invisible to our eyes.
- When white light hits a neutral-coloured surface, object or medium, and all wavelengths are reflected, it appears white to the observer.
About the observation of colour
- The human eye is sensitive to the visible spectrum, which includes all the spectral colours ranging from approximately 400 to 700 nanometers.
- The sensitivity of the eye to the visible spectrum enables us to perceive colours when light interacts with objects.
- The visual perception of colour by an observer is associated with words such as red, blue, yellow, etc., which are commonly used to describe hue or dominant wavelength.
- The colour an observer sees depends on:
- The wavelengths of visible light present in the environment.
- The wavelengths absorbed, transmitted, or reflected by an object or medium.
- The perception of colour can be affected by factors such as brightness, contrast, and saturation, which are related to the amount of light present in a stimulus and its interaction with the eye and brain.
- The observed colour of light is determined by its wavelength, not its frequency. However, as light travels from one medium to another, such as from air to glass, the colour seen by an observer may change due to refraction causing colours to disperse in different directions.
Related diagrams
Each diagram below can be viewed on its own page with a full explanation.
References
Things appear coloured to an observer because colour corresponds with a property of light that is visible to the human eye. The visual experience of colour is associated with words such as red, blue, yellow, etc.
- The colour an observer sees depends on:
- The range and intensity of wavelengths of visible light emitted by a light source.
- The path that the light takes and the different media and materials it encounters on its journey from its source to the retina of a human eye.
- Optical phenomena such as absorption, dispersion, diffraction, polarization, reflection, refraction, scattering and transmission.
- Predispositions of an observer such as their personal and social experience and cultural context.