On Wed, Feb 15, 2012 at 4:18 AM, Mike Harrison wrote= : > On Wed, 15 Feb 2012 02:34:27 -0500, you wrote: > > >1. It seems that some infrared LEDs also produce a very small amount of > red > >light. I powered some on, and looked at them directly for a few seconds > and > >saw a small amount of red light being emitted. Why does this happen? > > > >2. What are the effects of staring into a bright infrared LED for some > time > >(about the brightness of a bright flashlight that you normally couldn't > >look at for more than a few seconds)? Since you can't detect the light, > >you don't have that reflex to look away from the bright source. Does thi= s > >damage the eye if you continue to stare at it for some time (longer than > >you normally could into a bright flashlight)? > > It's not that the LED emits red, but some eyes have some sensitivity to > near IR. > The problem is that as the eye sensitivity is low, the amount of IR > entering the eye could be very > high, and can't be judged by the perceived intensity. > > I doubt a normal 20mA LED carries any hazard, but high power emitters and > laser diodes could well > cause damage. > Well the photopigments in the eye absorb light in the "visible spectrum" and molecules like retinal isomerize from 11-cis retinal to all-trans retinal and dissociate from the G-protein when a photon hits them. IR shouldn't cause the isomerization and dissociation from the G-protein and therefore energy isn't absorbed that way, so I don't think damage would occur that way. But how else can damage be done? Other than the heat transfer from the light, like burning from a LASER. Also, I do know that I have EXCELLENT vision, so I could be sensitive to some IR, good point. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .