2012考研英语阅读理解精读100篇【高分版】.pdf

TEXT ONE
William Illiam Morris (the wallpaper designer, rather than
the carmaker) suggested that nothing should have a place that is
not known to be useful or believed to be beautiful. Opals,
though, might be both. A group of researchers from the
University of Southampton, in England, and the German Plastics
Institute in Darmstadt, led by Jeremy Baumberg, have
discovered how to create a plastic with the gemstone's iridescent
properties. Their invention could be used to make a sparkling
substitute for paint, banknotes that are hard to counterfeit and
chemical sensors that can act as visible sell-by dates.
Opals get their milky sheen and rainbow sparkle from the
way light is scattered by the tiny crystals that form them. These
crystals are stacked in what is known as a face-centred cubic
structure. This means that the constituent atoms are arranged in
a lattice of cubes, with one extra atom sitting at the centre of
each cube's six faces. Light entering this lattice gets bounced
around in ways that generate colour by reinforcing the peaks of
some wavelengths and cancelling out those of others.
For many years researchers have been trying to develop a
synthetic material with the same light-scattering properties as
an opal, by etching patterns into various materials. That
approach has failed. Instead, Dr Baumberg has built his
opalescent material from scratch. He and his team grew tiny
polystyrene spheres until they were some 200 nanometres
across, before hardening them with a blast of heat. They then
coated the spheres with a sticky polymer before heating them
again. As the mixture was baked, the spheres moved naturally
into a face-centred cubic structure.
The result is a flexible film of crystals with opalescent
properties that can be used to coat malleable surfaces,
producing attractive iridescent hues. The size of the spheres can
be tailored to scatter particular wavelengths of light—a useful
property for security applications in wh