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Ultraviolet bulb...

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Hi
An incandescent light bulb; if its filament does not emit ultraviolet radiation, light passes trough its internal vacuum and then trough the glass that can contain tint, minerals, something in it. Can the resulting light be somehow ultraviolet, or contain some ultraviolet light by just passing trough a 'doped' glass ?
In other words, can light change its λ to ultraviolet by passing trough some tailored material ? Would that be similar to diode pumped solid state laser ?
 

You can filter OUT wavelengths but you can't add them in. You can possibly use the light to stimulate UV emission from a coating or substance added to the glass but it won't originate from the filament directly.

Brian.
 

Hi,

There are materials that can emit light of one wavelength when hit by light of another wavelength.

If I'm not mistaken then a neon lamp generates mainly UV light, but the inner coating at the glass tube modifies it to visible light.
So the other way round of what you describe.

Klaus
 

1.
I had a 'suntan' bulb which emitted UV light. Incandescent, a few hundred W. After running for a minute or two it got brighter and its color turned slightly bluish, which indicated it began giving off UV light.

2.
'Black light bulbs' are low-cost UV lamps going back to the psychedelic era. Incandescent type. I suppose the filament is ordinary tungsten. The glass has a dark blue coating which passes UV. Some visible light gets through and illuminates the room, although fluorescent colors are brighter due to the UV.

s-l300.jpg
 

You can get UVC LED bulbs cheap with ? 50W in edison style.

FL tubes emit UV and fluorescent dies 2 or tri-phosphor types always produce longer wavelengths , never shorter. Same with White LED's

Tungsten cannot produce UV significantly by any method except when imploding on failure with inert gas, not a vacuum.
 

There is some (very little) black body radiation in the UV from a filament bulb. Halogen better than argon bulbs.

The purple coating just makes it look like it could be effective but it isn't, very.

There are frequency doubling nonlinear optical materials (such as back in the day, first green solid state lasers were IR diodes with a doubler slab ).

Today you can get UV LEDs up to UV-C. Big win on lifetime, price at the shorter wavelengths not so much.
 

Halogen light bulbs give off some UV light. is this what you are referring to?
the better ones have a uv filter on the bulb or the light fixture to filter that out
 

I'm sorry but some of what is said here doesn't sound right. Normally you cannot "upconvert" light except in some rare cases with special substances that posses such physical properties
https://en.wikipedia.org/wiki/Photon_upconversion
Why? Because light wavelength aka frequency is directly proportional to the energy of the photons.
If you have a bulb like incandescent the maximum temperature of the filament determines the peak wavelength emitted because the filament is a black body radiator and the light output frequency is just the result of the thermal energy of the material.
Glass can only block UV not produce it because where would the energy come from?
In fluorescent tubes the mechanism for light emission is electron excitation within the mercury vapor due to current passing through the tube. As the excited electrons fall back to their original energy levels they give off characteristic energy photons. Mercury vapor under such excitation produces photons in the UV range. These photons then strike the phosphorus coating which illuminates. The glass envelope made from ordinary glass then shields the remaining UV portion and lets out the lower visible wavelengths.
In the special UV tubes there simply is no phosphor coating and the glass envelope is made from quartz so it passes the UV directly made within the mercury vapor arc right through the glass and out the lamp.

As for the claim that incandescent bulbs produce UV it is wrong, think about it, they barely even produce visible light at the temp they are operating in, because if you take the temperature of the filament and calculate the corresponding light wavelength you actually get the infrared range which is why incandescent bulbs are so inefficient as they produce 95% heat and only about 5% visible light for the power they consume
https://www.omnicalculator.com/physics/wiens-law

If you wanted UV from a blackbody element the filament would need to be heated to roughly 6000 Celsius because UV is roughly double the energy of visible light.
No metal is able to operate at such temperature. Incandescent bulbs only produce a brief flash of UV at the exact moment they burn out and that is also not because of filament temperature but because of the brief electric arc that forms and electric arcs tend to produce UV as they are very hot and also depending on the gas in which they are formed.
Fluorescent tubes on the other hand don't emit by black body spectrum they simply have sharp spectral lines due to the nature of their emission so the output is actually a sharp narrow peak of wavelength that then gets attenuated to wider and lower wavelengths with the help of the phosphor coating and glass envelop.
The early tubes actually had very sharp output which wasn't that eye friendly also they emitted some UV which got through.
 
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