• Question: Why is the rainbow in that order?

    Asked by to Edward, Ian, Mathew, Naomi, sakshisharda on 17 Jun 2014. This question was also asked by .
    • Photo: Ian Stephenson

      Ian Stephenson answered on 17 Jun 2014:

      When light goes from one material to another, it typically gets refracted – it changes direction. How much it changes is dependant primarily on the materials involved (their refractive index). However it also depends on the frequency of the light. Different frequencies of light get bent different amount (called dispersion).

      When light of a specific frequency hits your eyes it gets picked up by (typically!) three different types of sensors called cones. Each has different sensitivity to different frequencies of light, and out brain turns these into colours.

    • Photo: Naomi Osborne

      Naomi Osborne answered on 17 Jun 2014:

      All of the colours of the rainbow make up visible light – you may have seen this when using a prism to refract, or bend, light.

      When you use a prism to bend light, the different colours seen have different wavelengths – red has the longest, and violet the shortest and so these colours are bent slightly differently.

      When it rains, water droplets act like a prism, refracting light from the sun. When light is bent, its speed slows down and longer wavelengths like red slow down the most, causing it to be refracted the most and causing violet to be refracted the least – this is why you see the colours in that order.

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