US researchers say they have developed a technique that can significantly improve the efficiency of the traditional incandescent lightbulb, recycling the waste energy and focussing it back on the filament where it is re-emitted as visible light.

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US researchers say they have developed a technique that can significantly improve the efficiency of the traditional incandescent lightbulb, recycling the waste energy and focussing it back on the filament where it is re-emitted as visible light.