They make UV LED's, I use some. The compact fluorescent lights operate the same as standard fluorescent - a trace amount of mercury in the argon plasma emits UV that the glass coating converts to visible light. If you have a UV detector, it's easy to see all fluorescent lights "leak" UV. But, the amount of UV is only a small fraction of that produced by sunlight - even when inside on a cloudy day.
I find the incandescent bulbs work better for fine work using a magnifying visor, mostly because the lamp can easily be brought closer to the work. Banning incandescent bulbs was a 'group think' bone headed idea. Fortunately, rough service bulbs and similar - which are more suitable for machine work - are (currently) exempt from the non-sense.
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--- In 7x12minilathe@..., Bruce Freeman <freemab222@...> wrote:
John is correct.
However, the best UV-absorber for lamps is glass. "Flint glass" or sodium
calcium glass. The most common, cheap glass around. Put a glass mason jar
around your compact fluorescent lamp and NO UV will escape. Flint glass is
opaque to UV.
LED's and incandescent lamps (e.g., halogen lamps) do not emit enough UV to
worry about, As a rule of thumb, if the light originates with an electric
arc (as it does in fluorescent lamps), then UV is produced. Otherwise,
not. LED's are designed to emit the more easily accessible red, green, or
blue parts of the spectra. (UV is higher energy and presents design
challenges. Perhaps someone someday will make a UV-emitting LED for some
specific purpose, but it won't be used for ordinary lighting.) Incandescent
lamps, as John says, have an energy profile that just doesn't get up into
the UV.
On Mon, Oct 17, 2011 at 11:54 PM, john brookes <haiticare2011@...>wrote:
**
hmmm as an optical engineer, let me add my 2 cents about uv and lamps. Most
plastics will absorb uv and are good as filters. Exception is silicone and
thin acrylic. Regarding led emission of uv, their published spectra show
little or no uv even from blue types. In addition, they are encapsulated in
epoxy, which absorbs uv. The cf's do emit uv, but if you keep a shade
between you and direct exposure, no problem.
About uv from lamps causing cancer, I doubt it, since sunlight has much more
intense uv, and it takes long exposure times to get the skin destruction
seen in older beach bunnies. But its thought-provoking. The HF fluorescent
has a plastic cover over the cicular lamp.
Im surprised you say metal halogen bulbs emit uv, since the spectra of hot
emitters obeys a Planck spectrum which falls off steeply at high frequencies
with a peak according to Wien's law:
temp x wavelength = 3000. Thus a bulb at 3000 deg will peak at 1 micron,
whereas uv begins at .4 and above.
Im not sure you wanted to hear all this...
On a practical note, I notice shades I buy for floor lamps have plastic
liners which crumble after only a little use with cf - a typical sign of uv
degredation of the plastic. Based on that, Im leery of them. Anyone else
notice this?
john b
On Oct 17, 2011, at 10:29 PM, "Roy" <roylowenthal@...> wrote:
A lot of the relatively cheap, bright ones are phosphorized blue LEDs.
Roy
--- In 7x12minilathe@..., Jerry Durand <jdurand@> wrote:
On 10/17/2011 07:36 AM, lists wrote:
UV is certainly harmful to the skin and eyes, the $64,000 question is
whether manufacturers take the issue seriously and provide filter
coatings on the outside of the tubes.
Just to toss another wrench into the gears of life, many if not most
white LEDs are actually UV LEDs with the same type phosphors* in the
plastic as a florescent light has. So they, too, can emit UV.
* some use quantum dots instead. A very few will use multiple LED die
in 3-5 colors, but that's normally only in devices that are color
changing or for video/film lighting.
--
Jerry Durand, Durand Interstellar, Inc. www.interstellar.com
tel: +1 408 356-3886, USA toll free: 1 866 356-3886
Skype: jerrydurand
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Bruce
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