Luminescence: Difference between revisions
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'''Luminescence''' then is emission of light that comes from, well, roughly anything other than being at high temperature. | |||
{{comment|(For context, [[incandescence]] is light from being at high temperature, like [[black-body radiation]] or [[fire]])}} | |||
We could split | We could split luminescence into | ||
but we usually care about the few useful and/or common ones, seen in everyday life and/or products. | a handful of overall categories, | ||
and then into even more technical ones, | |||
but we usually care about the few useful and/or common ones, | |||
seen in everyday life and/or products. | |||
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* '''Photoluminescence''' - is light that is emitted due to absorption of photons (of a different wavelenth). Basically two variants: | * '''Photoluminescence''' - is light that is emitted due to absorption of photons (of a different wavelenth). Basically two variants: | ||
: '''fluorescence''' | : '''fluorescence''' | ||
:: will absorb light, and emit it at a higher wavelength | :: will absorb light (of varied wavelengths), and emit it again, at a higher wavelength | ||
:: will stop glowing almost immediately | :: will stop glowing almost immediately - so you usually notice only the the actively powered variant, not the passive variant | ||
:: Examples: | :: Examples: | ||
::: happens a bunch in nature | ::: happens a bunch in nature | ||
::: 'optical brightener' | ::: 'optical brightener' detergents | ||
::: tonic water in reaction to UV, due to quinine | ::: more selective to UV: | ||
::: banknotes often have security features to check | :::: tonic water in reaction to UV, due to quinine | ||
:::: banknotes often have security features to check | |||
* '''Phosphorescence''' (actually two different mechanisms) | |||
:: will absorb light, and emit it at a higher wavelength | :: will absorb light, and emit it at a higher wavelength | ||
:: and will keep doing so for some time, unlike fluorescence | :: and will keep doing so for some time, unlike fluorescence | ||
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* '''Chemiluminescence'''[https://en.wikipedia.org/wiki/Chemiluminescence] - light that comes from a chemical reaction | * '''Chemiluminescence'''[https://en.wikipedia.org/wiki/Chemiluminescence] - light that comes from a chemical reaction | ||
: For example, | : For example, | ||
:: '''[https://en.wikipedia.org/wiki/Luminol luminol]''' | :: '''[https://en.wikipedia.org/wiki/Luminol luminol]''' plus an oxidizing agent makes light. | ||
::: school demonstrations with it will use hydrogen peroxide for a strong and dramatic effect | ::: school demonstrations with it will use hydrogen peroxide for a strong and dramatic effect | ||
::: you may recognize the name from TV series with crime scenes. Blood is an oxidizing agent, you can detect trace amounts of blood (in a dark room, faintly, within the first 30 seconds of spraying. TV exaggerates this a lot.) | ::: you may recognize the name from TV series with crime scenes. Blood is an oxidizing agent, you can detect trace amounts of blood (in a dark room, faintly, within the first 30 seconds of spraying. TV exaggerates this a lot.) | ||
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* '''Electroluminescence'''[https://en.wikipedia.org/wiki/Electroluminescence] - something that lights due to passing current or an electric field | * '''Electroluminescence'''[https://en.wikipedia.org/wiki/Electroluminescence] - something that lights due to passing current or an electric field | ||
: is usually a semiconductor effect | : is usually a semiconductor effect | ||
: Examples: | : Examples: LED, OLED, [[EL wire]], light-emitting capacitors, and more, many for slightly different reasons | ||
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=="Glow in the dark"== | =="Glow in the dark"== | ||
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People use "glow in the dark" to refer to both fluorescence and phosphorescence. | People use "glow in the dark" to refer to both fluorescence and phosphorescence. | ||
* fluorescence - the things that light up under something like UV, perhaps best known for things light up in clubs | |||
:: Not just UV, but we associate them with UV in part just because the UV source can be fairly strong without being very visible to us, | :: Not just UV, but if it's visible light making other visible light, it would just be... a color - we wouldn't notice it. We associate them with UV in part just because the UV source can be fairly strong without that being very visible to us, so this is a case where we see ''only'' the reaction. | ||
so we see ''only'' the reaction. | |||
* phosphorescence - the things that persist for a while (e.g. the faint green stars we had on ceilings as kids) | |||
:: if holding something under a light for a bit makes it visible in the dark for a minute, it's this. | :: if holding something under a light for a bit makes it visible in the dark for a minute, it's this. | ||
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[[Category:Physics]] | |||
Latest revision as of 15:33, 6 April 2024
✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.
(Not to be confused with luminance, a descriptive 'amount of light' term that lives in the area of illuminance, luminance, brightness)
Types of luminescence
✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.