Why are things the colour they are

Everything we can see has a colour.

Around us, in our homes, at work, in nature, in space - it is universal. But have you ever thought about what makes something the colour it is?

The colour of anything we observe depends upon a few factors. Firstly - everything is made up of electrons and atoms.

How something looks when bathed in light is governed by these atoms and electrons. Different materials and objects have different makeups of atoms and electrons. Any object, by its nature, will, when exposed to light, do one of the following:

• Reflect or scatter light (reflection and scattering)
• Absorb light (absorption)
• Do nothing (transmission)
• Refract light (refraction)

Reflection and Scattering

A lot of objects reflect light to some degree, but something particularly reflective has more free electrons that can move easily between atoms.

These electrons vibrate and emit the light energy at the same frequency as the incoming light, rather than passing it to other atoms.

Absorption

Opaque objects absorb most incoming light. The electrons in the material absorb the energy, leaving very little reflected light.

Transmission

Transparent materials let light pass through because the light’s energy does not match the vibration frequency of the electrons. The light wave continues through the material unchanged.

Refraction

Refraction occurs when light slows down in a material, changing its direction. The light interacts with the electrons, causing slight vibrations and bending as it exits the material.

An Example: Why Natural Objects Are Coloured

Tomatoes appear red because they contain the carotenoid Lycopene, which absorbs most light but reflects red wavelengths.