# Do we have a resident physisist?



## fxstsb (Feb 19, 2008)

Is it harmful to look at 350nm through a defraction grating spectroscope?


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## NA8 (Feb 20, 2008)

You should ask over in the LED or GENERAL LIGHT DISCUSSION forums. More traffic there.


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## 65535 (Feb 20, 2008)

It's very dependent on the intensity of the source.


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## fxstsb (Feb 20, 2008)

NA8 said:


> You should ask over in the LED or GENERAL LIGHT DISCUSSION forums. More traffic there.



Thank you but it was moved here by a moderator


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## IMSabbel (Feb 20, 2008)

fxstsb said:


> Is it harmful to look at 350nm through a defraction grating spectroscope?



Depends on the intensity.
Generally, 350nm is already in the energy range that starts to become ionising. So you might expect typical "welder eye" problems.

If its just a single non-power LED, or the UV spectrum part of a (not to strong) halogen lamp, no problem.
If, otoh, its something like a 100W mercury vapour lamp, or an unshielded hid, please let it be.

Basically, there is no difference between using the grating monochromator and looking directly at the source. Of course, opposed to prismas, you have to be careful when using higher orders: You might get invisible light from lower defraction orders without noticing it.


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## The_LED_Museum (Feb 20, 2008)

If you're just looking at the 350nm line and little or none of the other light gets through, you might be playing with fire because your iris will be opened much more than it would be with visible light; thus exposing your eye to more UVA radiation than it might otherwise receive.


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## fxstsb (Feb 20, 2008)

What I wanted to do was select LEDs in that spectral range for custom lights. So maybe if I use the Difusion Spectroscope, maybe I need to observe the results thru a camera. What od you think?


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## 65535 (Feb 20, 2008)

If they are LED's just run them at low current and use your spectroscope.


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## yaesumofo (Feb 22, 2008)

*Re: Do we have a resident physicist?*

Don't you think that a lower current may alter the spectral output?
_If he want to cherry pick emitters to work at a specific wavelength It would make sense to me to test at the driver power unless it can be established that a lower current drive does not alter the wavelength._
_Just my 2.3 cents worth._
_Yaesumofo_

Oh and BTW please use extreeme care when looking at bright emiters regardless of the wavelength. A cool flashlight is no good reson to have permenantly dammaged vision.



65535 said:


> If they are Leds just run them at low current and use your spectroscope.


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## fxstsb (Feb 23, 2008)

*Re: Do we have a resident physicist?*



yaesumofo said:


> Don't you think that a lower current may alter the spectral output?
> _If he want to cherry pick emitters to work at a specific wavelength It would make sense to me to test at the driver power unless it can be established that a lower current drive does not alter the wavelength._
> _Just my 2.3 cents worth._
> _Yaesumofo_
> ...



Yo! Mo,
That is why I made the post to find out what my limits may be before doing the deed. 73


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## liveforphysics (Mar 19, 2008)

I've looked at lots of UV light sources through scopes. Tip the emmiter off axis a bit to reduce intensity if you are worried about it. Spectrum will be nearly uniform reguardless of angularity. For your eyes, 350nm is not really much different than visible light. This is another of those things where extreme prolonged exposure or very high intensity can cause a problem, just like with any light source. The trick with UV is that you don't recognize you are getting high intensity exposure, which is why people often have problems when dealing with it.

-Luke


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