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A LED is a long-lived light source, but certain mechanisms can cause slow loss of efficiency of the device or sudden failure. The wavelength of the light emitted is a function of the band gap of the semiconductor material used; materials such as gallium arsenide , and others , with various trace doping elements , are used to produce different ...
The appearance of objects illuminated by that light may vary as the spectrum varies. This is the issue of color rendition, quite separate from color temperature. An orange or cyan object could appear with the wrong color and much darker as the LED or phosphor does not emit the wavelength it reflects.
In CC drivers, the voltage changes while the current stays the same. CC drivers are used when the electrical load of the LED circuit is either unknown or fluctuates, for example, a lighting circuit where a variable number of LED lamp fixtures may be installed. As an LED heats up, its voltage drop decreases (band gap decrease [1]). This can ...
Diagram showing three lemon cells wired together so that they energize the red light-emitting diode (LED) at the top. Each individual lemon has a zinc electrode and a copper electrode inserted into it; the zinc is colored gray in the diagram. The slender lines drawn between the electrodes and the LED represent the wires.
Laboratory sources of UV are based on xenon arc lamps or, for more uniform but weaker light, fluorescent lamps. [8] More specialized sources include ultraviolet lasers [9] and synchrotron radiation. [10] Schematic of the experiment to demonstrate the photoelectric effect.
[22] [23] This is believed to be a unique example in physics of where such a fundamental law is invoked to explain two such different phenomena. [ 24 ] Albert Einstein noticed that the two situations both corresponded to a relative movement between a conductor and a magnet, and the outcome was unaffected by which one was moving.
They consist of a photocathode that emits electrons when illuminated, followed by a series of dynodes that multiply the electron current through secondary emission. PMTs offer high sensitivity and are used in applications that require low-light detection, such as particle physics experiments and scintillation detectors.
The laser diode chip removed and placed on the eye of a needle for scale A laser diode with the case cut away. The laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power.