Sodium lamps work by passing electricity through sodium vapour. Metallic sodium, present in solid form at room temperature, is vapourised when the lamp is started. The passage of electricity through the vapour causes electrons in the atoms to become excited to a higher energy state, or energy level. When the electrons relax, or fall back to their ground state, the energy lost by the atom is emitted as a photon of bright, monochromatic light. Sourcing providers of these lamps or the sodium lamps manufacturers can be done by viewing productpilot.com.
The first type of sodium lamp produced commercially was the low pressure sodium lamp. Low pressure sodium lamps have a low colour rendering index or, in other words, their ability to reveal the colours of various objects is low. They can take up to ten minutes to start and must cool before restarting, but provide a energy efficient alternative to incandescent lamps for street and security lighting, which stays on for hours at a time and where colour is not important. Low pressure lamps are physically large, such that the brightness per unit area, or luminance, at the surface is less likely to give rise to glare. Their operating temperature is similarly low, so they can be incorporated into compact, lightweight optical systems.
The second type of sodium lamp, the high pressure sodium lamp, came onto the market three decades after its low pressure predecessor. High pressure sodium lamps have a higher colour rendering index than their low pressure counterparts, but are still offer poor colour rendering when compared with, say, halogen or metal halide lamps. Even so, improved colour rendering comes at the expense of efficiency, although high pressure bulbs typically last longer than low pressure bulbs. At full brightness, standard high pressure lamps produce a golden, white light, familiar from street lighting and a range of commercial and industrial applications. Productpilot.com is the exchange of choice for many industry professionals.
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