• Question: What is colour-blindness and how does it work? Would you classify it as physics or biology?

    Asked by u12tsangv to Susan, Simon on 18 Nov 2013.
    • Photo: Simon Langley-Evans

      Simon Langley-Evans answered on 18 Nov 2013:

      Hi u12sangv

      It is most definitely biology. The reason we see at all is because we have cells at the back of the eye called rods and cones. Rods pick up black and white, while cones are responsible for colour vision. There are three types of cone cells and each type has a different sensitivity to light wavelengths. One type of cone perceives red light, another perceives blue and the third picks up green. The signals from these cells are handled by the brain which blends them together to give us a view across the full spectrum.

      People have colour blindness because they lack one or more of these cone cell types. Most people that we describe as colour blind lack the red and green cones and so cannot tell the difference between those colours.

    • Photo: Susan Skelton

      Susan Skelton answered on 19 Nov 2013:

      Hi again u12tsangv!

      We see things by detecting light that is reflected by them and then enters our eyes. At the back of the eye there are different types of cells which detect light: there are rod cells which distinguish between black and white, and there are three different types of cone cells – each type of cone cell detects either red, green or blue light.

      People who are colour blind usually have a problem with one or more types of cone cells so that they have no sensitivity to that colour.

      I think it’s difficult to classify subjects like these as either physics or biology as it lies somewhere between the two! You could say that it’s biology as it deals with living creatures (people!) or you could say that it’s physics because it deals with light.

      Research in this area is generally called biophysics, and there are lots of researchers (both scientists who trained in physics and those who trained in biology) working on these types of problems. One of the most interesting questions scientists are working on is how the molecules in the cells at the back of the eye actually detect the light. Scientists think that this can be explained by some complicated quantum physics, but it’s only just starting to be understood!

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