CORDELIA MOLLOY / SCIENCE PHOTO LIBRARY CORDELIA MOLLOY / SCIENCE PHOTO LIBRARY
Energy-saving light bulb. This compact fluorescent light bulb consists of phosphor-coated glass tubes which contain inert gas and mercury vapour. When electricity flows through the tubes, the mercury gas is excited and causes the phosphor to emit light. Normal filament (incandescent) bulbs only produce 10% of their energy as light, the rest is heat. Compact fluorescent bulbs produce much less heat than filament bulbs so more of the electrical energy is converted to light, making them more efficient.
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