• Question: How do pigments cause us to see something in a certain colour when colour is dependent on wavelengths of light?

    Asked by delaram123 to Dilwar, Lou, Rachel, Simon, Susan on 16 Nov 2013.
    • Photo: Susan Skelton

      Susan Skelton answered on 16 Nov 2013:

      Hi delaram – great question!
      You are absolutely spot on about colour being dependent on the wavelength of light!

      Light that looks “white” (like light from the sun or from a light bulb) is actually made up of all different colours of light added together – red, blue, green, yellow, purple etc. When this light shines on an object, the object either reflects or absorbs some of the light. For example, a red apple reflects the red light and absorbs all the other colours. The reflected red light then goes in to your eyes, so you see the apple as being red!

      The pigments are the materials that control which colours are reflected and which are absorbed. They choose which colour depending on which wavelengths they are able to absorb.

      Paint is a specially designed material that uses tiny “nanoparticles” to reflect different colours of light. This is why objects coated in different types of paint look different colours!

      Does this answer your question?

    • Photo: Simon Langley-Evans

      Simon Langley-Evans answered on 16 Nov 2013:

      Great answer from Susan there Delaram. I don’t think that I can add anything much to that. Do take a look at things under moonlight or the orange of streetlight though. They look different colours to the way they look in daylight. Everything looks black and white in moonlight, and that is because the light reflected from the moon and back to Earth is just too dim for the colour receptors in our eyes to detect. Street lights often make everything look yellow or orange. That is because they emit light that is not the same as the ‘white’ light of the sun. The light is only the yellow/orange part of the spectrum, so only those colours can be reflected back to our eyes.

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