Light-emitting diodes--semiconductors that emit light when electricity passes through them--have been around since the 1960s.
Current Blu-ray lasers emit light in the blue part of the electromagnetic spectrum (about 405 nm wavelength).
FORBES: What is the Future of Optical Disc Technology and who will Use It?
And researchers have even modified plants so that they emit light.
Simply put, this means choosing lights that shine down, not up, and that emit light only in those parts of the spectrum that the human eye can perceive.
Thus your body and objects that are underneath your clothes will have a somewhat higher temperature than the surface of your clothes and will emit light of a different IR wavelength than the surface of your clothes does.
FORBES: Hack Your iPad To See Through Clothes? An April Fool's Prank With A Real Physics Lesson
Even something too small to emit visible light will probably give off radio waves and infra-red radiation (Jupiter does).
These can be made to emit white light by coating the device with a phosphor compound that absorbs part of the blue light and re-emits it as yellow.
But LEDs are made from a semiconductor material, and are able to emit much more light for the same amount of electricity.
Active galaxies emit jets of light - up to trillions of times more energetic than the light we see - and a blazar is one with a jet pointing toward the Earth.
It was also a big week for lighting news as we learned that compact fluorescent light bulbs emit potentially harmful UV radiation -- another good reason to make the switch to LEDs.
Fluorescent bulbs emit a pallid, bleached light that is okay for hallways and porches, but which fails to flatter and provide a good quality of light for living rooms.
It will be lit by LEDs at the tips of the structure, but the council has asked for more detail on how much light they will emit as a condition of any approval.
Mercury arc lamps (the kind used in football stadiums) are not much better, since they emit a lot of ultraviolet light, which contributes to astronomers' woes without illuminating the action in a way that the human eye can detect.
In a report in the journal Nature, US researchers say they have worked out how black holes emit jet streams of particles at close to light speed.
应用推荐