LEDs
LEDs have become ubiquitous in this 21st century.
The scientific phenomenon of Light Emitting Diodes (LEDs) was first discovered in the first decade of the 20th century, and the first LED was created in the 1920s.
When I was in graduate school studying architectural lighting in the first decade of this century, LEDs were finally in practical commercial development. At the time, their colors were inconsistent and unstable, and they were not very bright. One look into the flashing lights of a typical ambulance, or a look at the colorful skylines of nighttime cities will convince any skeptic that LEDs are here to stay. They have transformed modern life.
The most impressive thing about LED bulb is that by combining red, green, and blue (and sometimes white) LEDs in the same bulb, virtually any color of the color spectrum can be created. Literally. This ability, of course, requires specialized circuitry within the LED lamp plus a user interface to program colors. This versatility, however, is something no other light source can offer.
There are now available "replacement bulbs" for many types of incandescent bulbs. These are LED bulbs that are designed to look (more or less) like the incandescent bulb one may be trying to replace. In practical terms, many have the screw-in bases to accommodate the bases used by incandescent bulbs.
Here, again, I have a few points to keep in mind when purchasing LED lamps:
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Aim low, in wattage. LED lighting is 5-6 times as efficient as incandescent lighting, meaning one needs one-fifth or one-sixth the wattage in LED lighting to get the same luminance as an incandescent bulb.
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LED lighting has not only superior efficiency compared to incandescent, but also much longer life. Dimming is to reduce output intensity, not to lengthen the lifetime of the bulb.
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Unlike other forms of electric lighting, LED bulbs do not simply fail (stop delivering illumination) with age. They will simply dim over time (5 years or more). An LED bulb is deemed ready for replacement when its output has diminished to 80 percent of its original output.
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Warm white bulbs are, for the most part, preferable in residential usage. Cool white may be useful as task lighting, as they tend to provide a more vibrant light.
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Electronic dimmers are essential for LED lighting, and it's imperative that the dimmer and the lamps/fixtures be compatible. Manufacturers will offer guidance to ensure there is no flicker or response delay upon turning on a light.