nanometers (was: AW: Uranus phaser)

[Martin Czech]

> 
> 	>> - Typical CdS LDR's are most sensitive to green light, just like
> the
> 	>> human eye. Using a green LED, especially an ultra-bright green
> LED,
> 	>> will make the current used to drive the LED much lower. 
> 	>> 
> 	>??
> 	>I have seen sensitivity measurement diagrams that show two peaks of
> 	>equal hights for CdS:  at green 540nm AND orange/red 640nm. 
> 
> I think CdS is only one of several materials for LDRs.
> There's CdSe (sp?), and probably mixtures of both.
> I have no idea what these surplus parts are made of.

There are (according to book):
CdS  operate in visible light
CdSe     ""

PbS   operate in infra red
PbSe            "
InSb            "
Hg(n)Cd(m)Te    "

The text says further, that allmost all photoresitive devices for
visible light use CdS.

> 
> 	>So these
> 	>very bright orange/red diodes should be sufficient, they are much
> 	>brighter then any green led I've ever seen, indeed one should not
> 	>directly look into the light source, danger of eye damage !
> 
> Is this really true? I think that even if there would be danger
> when you look at it with an optical device (telescope ...),
> it would have to be labelled so. (At least in Germany)
> Just wondering.
> 
>
I read this in a catalogue text, these diodes already have some kind of
optical lens, the radiation angle is quite narrow. Very, very bright
indeed, make a visible spot on your hand at 30 cm distance even in
daylight. Never looked directly into the beam thogh, I already have bad
eyes 8->.