• Question: why can we see through glass/

    Asked by andrewmoth to Chris, Eva, Michael, Paddy, Philip on 17 Jun 2011.
    • Photo: Chris Jordan

      Chris Jordan answered on 15 Jun 2011:

      The wavelength of visible light doesn’t match any of the energy levels of the glass molecules. Coloured glass is made when you put something in it that absorbs just some wavelengths of light leaving the rest to go through.

    • Photo: Eva Bachmair

      Eva Bachmair answered on 15 Jun 2011:

      Didn’t know that. But I do remember something from a lecture at Uni in food sciences when we were all quite amazed that glass is actually liquid and not solid. (sorry physics, if I didn’t get that in the right terms). You can see that when you look at really old windows like the ones you see in a church for example; they are thicker at the bottom.

    • Photo: Philip Denniff

      Philip Denniff answered on 15 Jun 2011:

      A great answer Chris.
      I think the only naturally occurring glass is obsidian that forms when lava from a volcano cools really quickly, before it has time to crystallise. It was prized during the stone age for making arrow heads because like glass today it can worked into a very sharp edge. (Obsidian looks black and shiny and will only let a little bit of light through it when it is very thin.)

    • Photo: Michael Wharmby

      Michael Wharmby answered on 16 Jun 2011:

      Yay a physics question – nice! 🙂
      I agree with Chris. Light passes through glass without being absorbed by anything in it, so we can see through it. Things like bricks are not see through because all of the light is adsorbed by the material and then it is re-emitted in all directions (scattered). Shiny things are shiny because they adsorb the light and re-emit it at an angle equal to the direction it came in at (reflection).

    • Photo: Paddy Brock

      Paddy Brock answered on 17 Jun 2011:

      Nice guys, not much for me to add here. But a challenge for the students… given the information above, can you explain why we can’t see through a leaf AND why the leaf appears green?

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