How can the same bulb come in 2700K, 3500K, 4700K?
Is there a different gas pressure, or gas mixture that increases or decreases this?
I would also be interested in an informed answer, I always thought that the Temp in K indicated the color of the light. the higher the temp the closer to white. but I may be getting that confused with CRI. Try Chp 9 in American Electricians HB. Mines packed away.
No just different elements in the gas mixture,
How can the same bulb come in 2700K, 3500K, 4700K?
Is there a different gas pressure, or gas mixture that increases or decreases this?
So the gas mixture is different then....
Would it be possible to use one set gas mixture, and change the color via voltage input?
How can the same bulb come in 2700K, 3500K, 4700K?
Is there a different gas pressure, or gas mixture that increases or decreases this?
How Television Works
by Marshall Brain
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Please copy/paste the following text to properly cite this HowStuffWorks article:
Brain, Marshall. "How Television Works." 26 November 2006. HowStuffWorks.com. <http://electronics.howstuffworks.com/tv.htm> 26 September 2009.
Inside this Article
Introduction to How Television Works
TV Pixels and Your Brain
TV Motion and Your Brain
The Cathode Ray Tube
Inside a CRT
TV Steering Coils
See more ?
TV Phosphors
The Black-and-White TV Signal
Painting the TV Screen
Composite Video Signal
Color TV Screen
Color TV Signal
TV Broadcasts
VCR and Cable Signals
Satellite TV Signals
Digital TV
Monitors vs. TVs
More Information on TV
See all TV Technology articles
Electronics Videos
More Electronics Videos ?
TV Phosphors
A phosphor is any material that, when exposed to radiation, emits visible light. The radiation might be ultraviolet light or a beam of electrons. Any fluorescent color is really a phosphor -- fluorescent colors absorb invisible ultraviolet light and emit visible light at a characteristic color.
In a CRT, phosphor coats the inside of the screen. When the electron beam strikes the phosphor, it makes the screen glow. In a black-and-white screen, there is one phosphor that glows white when struck. In a color screen, there are three phosphors arranged as dots or stripes that emit red, green and blue light. There are also three electron beams to illuminate the three different colors together.
There are thousands of different phosphors that have been formulated. They are characterized by their emission color and the length of time emission lasts after they are excited.
Producing a Photon
Any light that you see is made up of a collection of one or more photons propagating through space as electromagnetic waves. In total darkness, our eyes are actually able to sense single photons, but generally what we see in our daily lives comes to us in the form of zillions of photons produced by light sources and reflected off objects. If you look around you right now, there is probably a light source in the room producing photons, and objects in the room that reflect those photons. Your eyes absorb some of the photons flowing through the room, and that is how you see.
There are many different ways to produce photons, but all of them use the same mechanism inside an atom to do it. This mechanism involves the energizing of electrons orbiting each atom's nucleus. How Nuclear Radiation Works describes protons, neutrons and electrons in some detail. For example, hydrogen atoms have one electron orbiting the nucleus. Helium atoms have two electrons orbiting the nucleus. Aluminum atoms have 13 electrons orbiting the nucleus. Each atom has a preferred number of electrons orbiting its nucleus.
Electrons circle the nucleus in fixed orbits -- a simplified way to think about it is to imagine how satellites orbit the Earth. There's a huge amount of theory around electron orbitals, but to understand light there is just one key fact to understand: An electron has a natural orbit that it occupies, but if you energize an atom you can move its electrons to higher orbitals. A photon of light is produced whenever an electron in a higher-than-normal orbit falls back to its normal orbit. During the fall from high-energy to normal-energy, the electron emits a photon -- a packet of energy -- with very specific characteristics. The photon has a frequency, or color, that exactly matches the distance the electron falls.
There are cases where you can see this phenomenon quite clearly. For example, in lots of factories and parking lots you see sodium vapor lights. You can tell a sodium vapor light because it is very yellow when you look at it. A sodium vapor light energizes sodium atoms to generate photons. A sodium atom has 11 electrons, and because of the way they are stacked in orbitals one of those electrons is most likely to accept and emit energy (this electron is called the 3s electron, and is explained on this page). The energy packets that this electron is most likely to emit fall right around a wavelength of 590 nanometers. This wavelength corresponds to yellow light. If you run sodium light through a prism, you do not see a rainbow -- you see a pair of yellow lines.
So the gas mixture is different then....
Would it be possible to use one set gas mixture, and change the color via voltage input?
Different mixtures of phosphor coatings make the different colors. Fluorescent lamps make ultraviolet light. The phosphor changes the wavelength of this light to our visible spectrum. Most fluorescent have a mixture of 3 different phosphors to make a broader range of visible light.How can the same bulb come in 2700K, 3500K, 4700K?
Is there a different gas pressure, or gas mixture that increases or decreases this?
Temp in Kelvin does not measure "whiteness" of light. I heard of one firm in Las Vegas that has a wall of 20-30 white lights. When a client tells them they want white light they walk them over to the wall and tell them to pick which one they think is white. The higher Kelvin lamps are often marketed and sold as full spectrum, or similar to natural sunlight. This is just marketing BS to get your money.I always thought that the Temp in K indicated the color of the light. the higher the temp the closer to white.
The system for measuring light is not perfect but it's what we have to work with. Measuring the color of white light is odd when referencing this old experiment. I don't know of any better system.in the late 1800s, the British physicist William Kelvin heated a block of carbon. It glowed in the heat, producing a range of different colors at different temperatures. The black cube first produced a dim red light, increasing to a brighter yellow as the temperature went up, and eventually produced a bright blue-white glow at the highest temperatures. In his honor, Color Temperatures are measured in degrees Kelvin.
Actually, the phosphors don't "change the wavelength" of the UV, they fluoresce from being bombarded by the UV. All of the visible light comes from the coating glowing.The phosphor changes the wavelength of this light to our visible spectrum.
Sure it does.Actually, the phosphors don't "change the wavelength" of the UV, they fluoresce from being bombarded by the UV. All of the visible light comes from the coating glowing.
http://www.sylvania.com/Lighting101/LearnLighting/LightAndColor/FluorescentTechnology/This energy causes the phosphor coating on the inside of the tube to ?fluoresce,? converting the ultraviolet into visible light.
http://home.howstuffworks.com/fluorescent-lamp.htm/printableThis is where the tube's phosphor powder coating comes in. Phosphors are substances that give off light when they are exposed to light. When a photon hits a phosphor atom, one of the phosphor's electrons jumps to a higher energy level and the atom heats up. When the electron falls back to its normal level, it releases energy in the form of another photon. This photon has less energy than the original photon, because some energy was lost as heat. In a fluorescent lamp, the emitted light is in the visible spectrum -- the phosphor gives off white light we can see. Manufacturers can vary the color of the light by using different combinations of phosphors.