Luminous vs. Nonluminous Light Sources

In summary, phosphorescence and fluorescence are both forms of luminescence caused by the absorption of radiation. However, phosphorescence is more persistent and can last for a noticeable time after the stimulating radiation has stopped. A flashlight can be nonluminous if it does not emit visible light, but may still produce heat or other forms of radiation. In terms of safety, a phosphorescent light source would be safer to use in environments with explosive gas as it does not rely on heat for illumination.
  • #1
what is the difference between a phosphorescent source and a fluorescent source?

How does a flashlight can be luminous? How can it also be nonluminous?

Which kind of light source would be safest to use in building or mines that may be filled with explosive gas?
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  • #2
phosphorescence is more persistent (Websters)

might try webster's for starters:

flourescence is emission of EM radiation (usually visible light)
occurring ONLY DURING the absorption of radiation from some other source [quote from Webster's, with my emphasis on the only during]

phosphorescence is luminescence caused by absorption of radiation which persists for a noticeable time AFTER the stimulating radiation has stopped [my emphasis on the after]

phosphorescence can also mean a cold light from some chemical reaction, I believe, anyway some kind of production of light without noticeable amount of heat. But that is the secondary meaning.

the main thrust of what webster's has to say is that flour. and phosph. are pretty much the same idea-----just that phosphorescence is more persistent. Typically both are caused by absorption of some more energetic type of light-----UV for example.

A fluorescent light tube works by making UV inside the tube and having the UV get absorbed in a white coating on the glass and that coating shines with visible light---it fluoresces. And when you turn it off, the production of ultraviolet inside stops almost immediately and also the flurorescence stops.

But an example of phosophorescence are those plastic stars parents give children to stick on the bedroom ceiling. They get irradiated by ordinary room lights. Then you turn off the room lights and they glow this dim greenish white color for a while.
It lasts for a good 15 minutes, as I recall. Then you have to turn the lights back on to give it another dose of energy.

YOU SHOULD go to your local bicycle shop and have them explain
the nokia white LED bike headlight. That is a really great light source. It runs on, like a few volts of battery power. It is cool. No sparks, no hot filament. A beautiful idea----a blue solid-state light embedded in a yellow fluorescent plastic. Some of the blue comes thru and some of it excites the fluorescent dye in the plastic making it glow yellow. So what comes out is a mix of blue and yellow and it looks white. Find out, I urge you, it is a great light source---only on the market since 1998 or so, I think.
  • #3
I suppose phosphorescence originally meant the emission of photons from a source of phosphorus recently subjected to illumination. Phosphorescence now applies to any substance with such property.

Fluorescence may have originally applied to fluorine, an element so reactive as to produce light (and heat!) upon interaction with most substances. The current usage of "fluorescence" may apply to the production of light by direct application of chemical or other non-thermal energy.
  • #4
There's also incandescence, the property of a body so hot its blackbody radiation emits visible light. Obvious examples are ordinary tungsten lightbulbs, red ambers and so forth.
  • #5
Fluorescence happens when a substance absorbs one wavelength of light, and re-emits a lower one. (essentially, the Shorter wave length photon causes an electron to jump up a number of energy levels, and then the electron returns to its initail state, on energy level at a time.)

I believe it got its name from the mineral that first displayed this characteristic, this is the same mineral from which flourine was separated from, so flourine got its name form the same mineral. The Mineral was named after the region where it was first discovered.
  • #6
Phosphorescence differs from Fluorescence in the fact that it continues even after the initial light source is removed.

The term Phosphorescence comes from the Greek for "light bringing" (Which was also the name given to Venus when it was the Morning star).

Interestingly, phosphorus, which also gets its name from the same root, exhibits Fluorescence not Phosphorescence.
  • #7

how can a flaslight be nonluminous ?

1. What is the difference between luminous and nonluminous light sources?

Luminous light sources produce their own light, while nonluminous light sources reflect light from other sources. Examples of luminous light sources include the sun, fire, and light bulbs, while nonluminous sources include the moon, planets, and objects that reflect light, such as mirrors or white paper.

2. How do luminous and nonluminous light sources affect visibility?

Luminous light sources are typically easier to see in the dark because they produce their own light. Nonluminous light sources may be difficult to see if they are not reflecting enough light, but they can also provide visibility by reflecting light from other sources.

3. What are the properties of luminous and nonluminous light sources?

Luminous light sources emit electromagnetic radiation, also known as light, while nonluminous light sources reflect light. Luminous sources can vary in color, intensity, and wavelength, while nonluminous sources can vary in reflectivity and the amount of light they reflect.

4. Can nonluminous light sources become luminous?

While nonluminous light sources cannot produce their own light, they can become luminous if they are exposed to another light source. For example, a dark room with no light sources can become luminous if a flashlight is turned on inside.

5. How do luminous and nonluminous light sources affect the environment?

Luminous light sources can have a significant impact on the environment, as they can emit heat and UV radiation, which can affect living organisms and ecosystems. Nonluminous light sources, on the other hand, have a more indirect impact on the environment through their ability to reflect light and contribute to overall light pollution.

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