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A school science club has developed a sensor that allows water companies to
detect pollution on the spot rather than back in the lab. Pupils at Archbishop
Tenison鈥檚 School in Croydon, south London, and their teacher John Treadaway have
built a portable analyser based on a principle known as surface plasmon
resonance. Laser light reflected by a metal film on the back of a prism contains
a dark spot at a certain angle where the light interacts with the electrons of
the metal. This angle changes when pollutants such as metal ions or bacteria
stick to a chemical coating on the back of the film, moving the dark spot in the
reflected light. Thames Water is supporting further development of the
instrument.