What is White Light?
White light is the name given to what the human eye sees when all the colors that make up the visible light spectrum are combined; the visible light spectrum is made up of red, orange, yellow, green, blue, indigo, and violet light, and these colors combined make white lighting. When shined through a prism, white lights are broken into the separate colors of the visible light spectrum. Many people commonly refer to white light simply as "light" or "visible light," and it is this light that makes it possible to view one's surroundings. Several sources of white lights exist including the sun and stars, certain types of lightbulbs, and some lamps.
Sources
Incandescence, which is visible light created from heat, is the greatest known generator of white light. Objects with lower temperatures emit infrared radiation, which cannot be seen, but as an object gets hotter, the wavelengths get shorter and brighter, moving through red to yellow to white; these white lights are visible to the human eye. In addition to the sun and the common light bulb, molten materials, such as metal or glass, also glow incandescently.
Most light sources are thermal, meaning the type of radiation they emit is a characteristic of the source's temperature. Visible light is primarily radiated by the sun and many other stars. In fact, most of the energy radiated by the sun is within the visible spectrum, which is likely why human beings can see this range of light. Other white light sources include incandescent light bulbs, fluorescent lamps, halogen lamps, white LEDs, and flames.
Electromagnetic Spectrum
White light waves are part of the electromagnetic (EM) spectrum, which also includes radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. The only part of the EM spectrum that the human eye can see without the use of technology is the band of white, visible light. This spectrum is enormous, with waves that vary considerably in size; there are waves that are thousands of miles (kilometers) long, waves smaller than atoms, and everything in-between. Visible light exists in a very narrow band of the electromagnetic spectrum, between infrared (IR) and ultraviolet (UV).
It is the filtering of white light that gives objects color. The sky on Earth is blue because the air molecules filter much of the red light wavelengths out of the white light that comes from the sun. Objects absorb and reflect different light waves to produce all of the colors that can be seen.
Alternative Definition
Although it is a less common definition of the term, some holistic healers refer to white light as a part of the universe that stores all positive energy. By calling on the white light, it is believed that auras can be cleansed and protected from negative energy. Spiritual healers, yogis, and mystics are among those who attempt to connect with this light, often through prayer and meditation.
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![Fluorescent light bulbs emit white light.]()
By: tr3giFluorescent light bulbs emit white light. -
![When all of the visible spectrum is combined, the result is white light.]()
By: Peter Hermes FurianWhen all of the visible spectrum is combined, the result is white light. -
![To some holistic healers, white light can cleanse and protect auras from negative energy.]()
By: Nikki ZalewskiTo some holistic healers, white light can cleanse and protect auras from negative energy. -
![Spitual healers attempt to connect with white light through prayer and meditation.]()
By: memoSpitual healers attempt to connect with white light through prayer and meditation.
Discussion Comments
Just want to say that white light in the scientific community is not a general term. Digital TV, broadcast studios, photography, etc. all use very specific terms when referring to "white light" which is equal parts red, green, and blue. The sun emits white light but it is mixed with the blue of the atmosphere and becomes daylight not white light. Incandescent bulbs don't produce white light but we see white as white because our eyes have red, green, and blue sensitive cones that contract and expand to "accommodate" for the differences in color content which can be significant.
Original fluorescent was very high in green and requires a FL 1 or 2 filter to correct to a more white light source for photography. TVs produce white by emitting R,G, and B colors and sometimes combined with black for technical reasons. Also, TVs have adjustments to add and subtract amounts of certain parts of the spectrum during the emission phase to provide customers the tint and tone they prefer. Shine 3 projectors on a white card with pure colors of green light, one with blue light, and one with red light. Where ever all three lights hit the white background and overlap, you have white light.
To name several light bulbs, daylight, fluorescent light, etc. and call it white light is OK for general conversations but certainly not accurate in the real world.
Thanks for the info, although I'm looking for more of the rate of absorption between dark colours and light colours.
As a photographer it is critical for me to find light output that is "white." This is typically referred to as daylight. The full spectrum of light coming from our Sun is probably the closest thing we have to a pure white light.
You are right though @sammyG, the mood and setting can be easily effected by the color quality of the light. If I am going to photograph a subject and want a hard, cold edge, I will use a blue filter on my lights. The opposite of that is a warm or yellow/orange filter that can really add heat to a portrait.
I never realized how much the color spectrum of light can affect things like our mood. If you go to the store and look at light bulbs you will find an entire section of varying types. Some are described loosely as "warm" or "cool."
I prefer cool lighting in my kitchen and warm lighting in my living room. I wonder if any bulb is capable of producing a pure white light.
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