• Question: What makes something transparent? I know because transparent objects passes light through them but why does it pass light while opaque objects do not?

    Asked by rajathjackson to Dave, David, Jack on 27 Jun 2013.
    • Photo: Jack Miller

      Jack Miller answered on 27 Jun 2013:

      Hi Rajath,

      This is a great question, and one with a complicated answer. It’s all due to quantum mechanics. The following answer is approximately correct: if the structure in question is a crystal (like quartz) then there are a large number of well-defined energy levels that the electrons in the crystal can sit in. If photons are incident at an energy that is sufficient to promote electrons between these energy levels, they are absorbed. If they’re not of that right energy, they’re not. Whether or not something is transparent is therefore a function of its wavelength — the only thing (to my knowledge) that is transparent across the entire EM spectrum is the vacuum.

      Hope that helps!

      — Jack

    • Photo: Dave Farmer

      Dave Farmer answered on 28 Jun 2013:

      Hi rajath,

      There’s no way that I could explain this better than one of my lecturers already has, so listen to him:

      Hope that helps.