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Fluorescence intermittency, or blinking, is the phenomenon of random switching between ON (bright) and OFF (dark) states of the emitter under its continuous excitation.It is a common property of the nanoscale emitters (molecular fluorophores, colloidal quantum dots) related to the competition between the radiative and non-radiative relaxation pathways.
Fluorescent bulbs contain mercury, a toxic substance. The United States Environmental Protection Agency (EPA) provides safety guidelines for how to clean up a broken fluorescent bulb. [17] Mercury can be harmful to children and developing fetuses, so children and pregnant women should avoid being in the area whilst a broken bulb is cleaned up. [18]
Headlight flashing might have come into more common use as a means of attempting driver-to-driver communication by the mid-1970s, [3] when cars began to come with headlight beam selectors located on the steering column—typically activated by pulling the turn signal stalk—rather than the previous foot-operated pushbutton switches.
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]
The spectrum of light emitted from a fluorescent lamp is the combination of light directly emitted by the mercury vapor, and light emitted by the phosphorescent coating. The spectral lines from the mercury emission and the phosphorescence effect give a combined spectral distribution of light that is different from those produced by incandescent ...
Intentional light variations are applied for warning, signalling (e.g. traffic-light signalling, flashing aviation light signals), entertainment (like stage lighting) with the purpose that flicker is perceived by people. Generally, the light output of lighting equipment may also have residual unintentional light level modulations due to the ...
A street lamp mounted on a bracket and column A high pressure sodium street light fixture. Street light interference, sometimes called high voltage syndrome, is the claimed ability of individuals to turn street lights or outside building security lights on or off when passing near them. [1]
This layer also reflects the phosphor light to the desired direction, and protects the phosphor from ion bombardment resulting from an imperfect vacuum. To reduce the image degradation by reflection of ambient light, contrast can be increased by several methods. In addition to black masking of unused areas of screen, the phosphor particles in ...