This talk was created when I held the Teaching Fellowship of the Colour Group UK in 2008-2009. It is a demonstration-based talk about the science of colour. I've given this talk, with remarkably minor variations, to audiences ranging in age from about 9 to 18. As well as the Colour Group, subsequent funders for this talk have been the Royal Institution and Glasgow University Science Festival.
I have been reappointed by the Colour Group as Teaching Fellow for the year 2009-10.
The three themes of the talk are:
- What is it about light and the way it behaves that makes colour vision even possible? The essential answer to this question is that there are different kinds of light and that there are processes in the world that can either make these different kinds of light individually, or that can separate the different kinds of light from mixtures.
- What is it about our eyes and brains that enable us to distinguish the different kinds of light from each other, ie, to see in colour? The essential answer to this question is that we have more than one kind of light-sensitive cell in our eyes, and that these different kinds of cells are sensitive to different, but overlapping, parts of the spectrum.
- Why is it useful to a creature to be able to see in colour? Why is it advantageous to a creature or plant to be coloured, and why do people use colour? The evolutionary answer to both these questions is: because you'll have more babies. The second question applies in a special way to humans, because of our conscious use of colour for all sorts of purposes.
Into this structure are worked the following demonstrations (along with a number of images on slides):
- Newton's first experiment with a prism.
- Flame colours.
- Metameric illuminants demonstration. (Please note that the demonstration described in the link is not yet the lecture-scale demonstration that I actually use.)
- Mixing of coloured lights (additive colour mixing).
- Colour aftereffect using red and green patches to generate afterimages.
- The Bidwell effect. (Please note that the demonstration described in the link is not yet the lecture-scale demonstration that I actually use.)
- Simultaneous colour contrast.
- The checkershadow effect.
- The grey squares demonstration..
- Blackness is not the absence of light.
- How to make a black thing look white by taking light away.