• Question: What is a color?

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      Asked by The Ge Ni U S to Andrew, Jade, Jessica on 25 Jun 2015.
      • Photo: Jessica Wade

        Jessica Wade answered on 25 Jun 2015:


        Hey genius,

        tricky stuff this morning. A colour is what our eye percieves when light comes into it with different energies. There are light receptors in our eyes and they respond differently to different kinds of light. Light waves are wonderful things, and all travel at the same speed but with different energies. The different energies means they have different ‘colours’. We split the whole light spectrum (from X-rays to radiowaves and infrared) into different sections so we can understand it better. Microwaves and radiowaves travel at the same speed, but they each do different things better- radio waves are great for tunes, microwaves good for popcorn. There is one part of this spectrum called the ‘visible spectrum’- and these are where the colours of the rainbow all live (red-violet).

        Colour is all about electrons in different molecules jumping up and down. When the electrons make a jump up, they take in a bit of energy (if we heat the molecules up). They aren’t very happy or stable then, so quickly try to jump back down. When electrons jum down, they emit light. The size of their jump tells us about what colour the light will be. Really energetic light is blue (like ultraviolet light from the sun) and lazy light is red. The energy tells you about a property of the light called the ‘wavelength’.

        When light hits something that isn’t a source of light, some of the light is absorbed (it goes into the object and heats it up) and some of the light is reflected (it bounces off and hits our eyes). We can work out what colour an object will appear to us because of how that object would absorb the light (we can work out what colour it will reflect). A green apple isn’t actually green, but it is reflecting all the colours of light energy we see as ‘green’ and absorbing everything else.

        It’s crazy to think we only see colour because of little receptors in our eyes. These are called the ‘cones’. We have six million cones in each eye!

      • Photo: Andrew Fensham-Smith

        Andrew Fensham-Smith answered on 25 Jun 2015:


        A colour is what we see when a light of a specific amount of energy is detected by our eyes. We can only see a very narrow range of light energy, and we’ve split it up into different bits we call colours – high energy light we call blue light, and low energy light we call red light. If you’ve ever seen people develop photographs you’d see they do it in red light – this is so that the red light doesn’t ruin the photo film, which is sensitive to higher energy light like blue light.

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