Blue LED's similar to UV light?

[socom1970]

I have noticed when using my A2 blue LED's, some things that flouresce under UV light also flouresce under the blue LED's. (white clothing, brite-colored things like hi-liters, neon-coloured things, etc...) Do blue led's have similar wavelength/output to UV led's/lights? Is there any danger to using blue led's like there is with UV?

 

[KeyGrip]

Blue LEDs might actually put out some UV, but I'm not sure as I haven't looked at a graph lately. If they don't, then it's probably because the wavelength is similar. I don't think there's any real danger. Some makers make UV leds, and let's not forget about the crazy radiation that incandescents put out.

 

[coolwaters]

if u look a the wavelength chart u can see that some of the waves emitted are UV rays.

 

[elgarak]

Blue LEDs might actually put out some UV, but I'm not sure as I haven't looked at a graph lately. If they don't, then it's probably because the wavelength is similar. I don't think there's any real danger. Some makers make UV leds, and let's not forget about the crazy radiation that incandescents put out.

No. The wavelength of monochromatic LEDs is pretty narrow. Blue LEDs have typically ~450 nm, with a width of about 20 nm. They do not emit UV, which would be below 400 nm.

To make things fluoresce, you need light above a certain energy, or below a certain, fixed wavelength. The specific energy/wavelength is defined by the material that fluoresces. If it fluoresces with blue, then this wavelength is above 450 nm (or whatever the wavelength of the specific LED is). It would also fluoresce with UV, having a wavelength lower than the 450 of blue. But when the specific wavelength is between 400 and 450 nm, then it fluoresces ONLY with UV.

Everything that fluoresces with blue does so also with UV, but not the other way round.

 

[greenlight]

Well, blue is next to UV in the spectrum, so it has some of those properties.

Other color LEDs highlight certain items, too.

For example, my green LED flashlights highlight yellow caution tape particularly well, even though it is not phosphorescent. That can be useful in certain situations.

 

[xenopus]

As you have noticed, many fluorescent materials can be excited by both Blue (450-470nm) and UV (365-395nm, for example).

Blue will excite many man-made fluorescent materials, and, more importantly, organic evidence. The advantage of using Blue wavelengths when looking for evidence on fabric that has been washed with detergent that contains brightners (sheets, clothing, etc) is that the urine and semen will fluoresce, whereas the sheet or clothing article will not. Under UV, it may be the case that both fluoresce and "drown out" observable fluorescence of what you are looking for.

Since blue is visible, you will need good orange glasses to visualize the fluoresnce, which will otherwise be mostly blown out by the intense blue light source.

Like bags at the airport, many orange glasses look alike, but many will not perform in this application.

 

[Maglight240]

I have about 36" worth of Blue LEDs in my Pickup truck cab and the other morning I had some ear plugs on the dash, florescent orange, low and behold they were glowing like the sun in the cab of the truck. Blue LEDs do make some florescents glow.

 

[JoakimFlorence]

I noticed that a blue LED emitter can cause many fluorescent dyes/pigments in common household items to glow. Pink, orange, and yellow fluorescent colored objects all glow, but green fluorescent colored objects do not. (These fluorescent green colored objects all glowed under a black light tube)

Blue LED light can also make white clothing glow, but only faintly. The fluorescence of white clothing is much stronger with a violet wavelength LED.