A family of closely related terms underpins all the content at lightcolourvision.org and we aim for accuracy and consistency of usage as we demonstrate the connections between light, colour and vision.
We want our resources to be accessible to a general readership of students, teachers and researchers of all ages who want to build on their existing knowledge one step at a time.
Each term has its own page in the REFERENCES section and starts with a brief definition. Bullet points follow that aim to provide context.
Links embedded in the text of RESOURCES pages link to the definitions. Shorter summaries also appear on pages within the RESOURCES section entitled SOME KEY TERMS. The purpose of the summaries is to provide a quick reference stripped down to basics.
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When light strikes an opaque material the wavelengths that are not reflected are absorbed and their energy is converted to heat.
- When sunlight strikes an opaque object or material, it can be reflected or absorbed.
- If the light is reflected it bounces off at the same wavelength.
- If the light is absorbed, its energy is transferred to electrons which re-emit the energy as heat.
- Of the light that reaches Earth’s surface from the Sun:
- 54% is already heat (infrared wavelengths of light) before it reaches the earth’s surface.
- 45% is visible light.
- 1% is shorter wavelengths (ultraviolet).
- Absorption of a particular wavelength of light into a material takes place when the frequency of the wave matches the frequency of electrons within it. As electrons within atoms absorb energy and heat up they vibrate more vigorously causing the atoms to collide with one another.
- Because the electrons in different atoms have different frequencies they selectively absorb different frequencies of visible light.