• Question: Why is water clear?

    Asked by jess040897 to Andrew, Daniel, Hayley, Natalia, Peta on 16 Nov 2011.
    • Photo: Daniel Scully

      Daniel Scully answered on 16 Nov 2011:

      Because it doesn’t absorb visible light very easily.

      Light is part of a spectrum including gamma rays, x-rays, ultra-violet, visible light, infra-red, microwaves and radio waves.
      Different materials can absorb different parts of that spectrum more or less easily.

      Some liquids, like coke, are good at absorbing visible light. Others, like water, aren’t.

    • Photo: Hayley Smith

      Hayley Smith answered on 16 Nov 2011:

      Yup, it’s because water isn’t very good at absorbing visible light.

      It does absorb some visible light, but not very much at all. The colour (wavelength) of visible light that is absorbed the least by water is that at the blue end. That’s why if you get a big enough mass of water together (like a lake) it may look blue, but this effect is only noticeable when there’s a large mass, so more than would be in a glass.

    • Photo: Peta Foster

      Peta Foster answered on 16 Nov 2011:

      This is a great question!

      Water is clear because it does does not scatter or absorb the visible light that is incident on it. It does reflect some of the light as i am sure you have seen when looking at your reflection in a pool of water.

      However even though the water looks like the light is very simply passing through it as if it were not there… this is not the case. If you place a ruler into a bucket of water and observe it, it will look as if it bends going into the water. This is because the light changes direction when entering the water due to it being slowed down by the water medium…

      …why is the light slowed down? Well the light could just travel past a few atoms and not be effected but there are so many atoms around that the light is bound to get absorbed and re-emitted at some point and when that happens it produces a bit of a lag in the light wave and therefore slows it down overall.

      Hope this helps 😀

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