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New lighting systems have not used magnetic ballasts since the turn of the century, however some older installations still remain. Fluorescent lamps with magnetic ballasts flicker at a normally unnoticeable frequency of 100 or 120 Hz (twice of the utility frequency; the lamp is lit on both the positive and negative half-wave of a cycle).
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor coating in the lamp glow.
An electric discharge in the tube causes the mercury atoms to emit mostly ultraviolet light. The tube is lined with a coating of a fluorescent material, called the phosphor, which absorbs ultraviolet light and re-emits visible light. Fluorescent lighting is more energy-efficient than incandescent lighting elements.
Fluorescent lighting can be used as grow lighting, but it has limitations. Because fluorescent lights are not very intense or bright, they must be placed very close to the plants to overcome their ...
Fluorescent lamps using conventional magnetic ballasts flicker at twice the supply frequency. Electronic ballasts do not produce light flicker since the phosphor persistence is longer than a half cycle of the higher operation frequency of 20 kHz. The 100–120 Hz flicker produced by magnetic ballasts is associated with headaches and eyestrain. [8]
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A hawksbill sea turtle was recently found that is stumping scientists. The turtle was glowing, but not through bioluminescence like a firefly or plankton that turns tides blue. It's biofluorescent ...
Biofluorescence requires an external light source and a biomolecular substance that converts absorbed light into a new one. The fluorescent substance absorbs light at one wavelength, often blue or UV, and emits at another, longer wavelength, green, red, or anything in between.