Ex: Police Lightbars, they’re so bright but use so little of the cars battery. Much less than the classic rotating lights.
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You know a lot of light is invisible, right? Infrared, for example. You can’t see it, but you can feel it on your skin with your eyes closed when you’re standing near something really hot.
Take two lightbulbs that consume exactly the same amount of electric energy, but one produces only visible light, and the other products half visible light and half invisible. The second one will look much dimmer.
The old-timey incandescent filament lightbulbs, the ones that burn your fingers to the touch, they produce mostly infrareds! To the tune of 90%!
That’s why so much progress has been done. Because there was so much room for progress.
LED lights produce mostly visible light. Do this is it. There won’t be much progress anymore. We’re there. We can focus on other things now. Cool, hey?
There are a number of forms of energy. Light, heat, magnetic, chemical, gravitational, mechanic, sound… The most efficient way to make light is converting electrical energy straight to light energy. LEDs are best at this.
Old style lights work by heating up a something so it glows, giving off light. But glowing things will always give off most of their light as infra red, or, if you make it really, really hot, ultra-violet. Visible light makes up a small part of the spectrum of lights, so you can’t make these type of lights efficient.
Efficient lights, like fluorescent, sodium or mercury vapour, metal halide, high intensity discharge or LED, use methods other than just ‘something really hot’, to create only light that is in the visible spectrum. When you look at it this way, even these light sources are not really that efficient – turning less than 50% of the energy they use into light. But this handily beats ‘hot thing’ lights which are 5 to 10% efficient.
Incandescent lights work by black body radiation. Essentially, they get a piece of metal hot. Some heat gets radiated as energy. The hotter (and more energetic) the object, the more energy it radiates, and the more of that energy gets radiated at higher frequencies. So if you pump enough electrons into a piece of metal, it’ll get hot enough to glow in the visible light spectrum. But you’re wasting a bunch of energy by radiating in the infrared spectrum as well.
LEDs emit light in a much more straightforward manner. Basically, when electrons need to lose energy, they jettison it in the form of a photon. LED materials have “electron holes” of a certain “depth” so that electrons that “fall down” the hole emit energy in the desired wavelength. You’re basically directly converting electricity into the wavelength of light you want, instead of heating up metal to get light as a side effect.
Light gets emitted by electrons when they drop energy levels, emitting a packet of energy.
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