Here is a photo I recently took with my friend Tom. It’s a little tube containing a suspension of colloidal particles (described a bit more on my Science page). Colloids are small but not microscopically tiny, which means that when they form crystals, the typical distances between particles are larger than those found in molecular or atomic structures. In fact, the distances correspond roughly with the wavelength of visible light, so the crystals scatter incoming light of all different colours and, as shown in the picture, look great. Natural and synthetic opals also display this ‘opalescence’, because they are formed by the crystallisation of colloidal sand particles.
I got this little sample when I was on a conference in Corsica and I’m very fond of it, because the only colloidal suspensions I usually get to see are pretend ones in computer simulations. The motivation for having spent a morning with Tom pointing a camera at a tube is, hopefully, to provide a nice green-screen background for an interview I was involved in for the Physics Department’s website. In the interview I managed to talk for 15 minutes about why Leeds is a good place to do a PhD, while forgetting to once mention its music scene. Well done me.
Thanks very much to Tom West for his incredibly steady camera-hands, and patience.