• Question: How does a prisim seperate white light? Why isn't black/brown in the rainbow. And I heard that black is not a real colour or in nature and it is man made. Is that true?

    Asked by piwikiwi3 to Christina on 19 Jun 2013.
    • Photo: Christina Pagel

      Christina Pagel answered on 19 Jun 2013:

      Are you going to do GCSE or A-level physics? if so, you’ll learn all about that!! the colours you see in a rainbow (or the ones you get from shining light through a prism) are different wavelengths of light (you cna think of light like a wave with crests and dips and a wavelength is the distance between crests). Blue has a shorter wavelenght that red (ie its crests are closer together).

      Brown doesn’t have a single wavelength and so it’s not a true colour, but it can be made by mixing two true colours together (red and green i think).

      Black is the *absence* of light and so isn’t a colour either… black paint absorbs all the different wavelenths of light and so nothing is reflected back into your eyes (so the absence of light).

      There are some really cool experiments done showing how our brains have learned to interpet colours and mixtures of colours! Look at this – it’s brilliant : http://www.swamij.com/illusion-purple-dots.htm

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