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What happens if one looks directly at infrared LEDs? Sometimes I see this kind of LED at night as red dots and I'm also courious about it.

I was wondering what would happened if one looked directly to these LEDs, because we see them everywhere like in remote controls, CCTV cameras, sensors, etc.

What is the difference between infrared and visible light to our eyes? (I mean why is it impossible to look directly to visible light while we can look to infrared?)

  • LED: Light-emitting diode

Infrared LEDs

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Infrared wavelengths are EM waves of longer wavelengths than visible light. Also, visible waves are more energetic than IR waves.

Because of this, Visible light has the ability to excite organic receptor molecules in our eyes called Rods and Cones. These molecules stimulate cell responses and in turn excite cell responses in our nerves called an Action Response. Still unclear to most scientists is how the brain composes these action responses into an image, though a great deal of research is being done to date.

The reason why "nothing happens" when we aim infrared lights into our eyes (which I still wouldn't suggest) is that the photoreceptor molecules that we use to see don't have the necessary bonding configuration to accept the energy from these impinging EM waves.
However, don't go thinking that nothing happens. Infrared radiation is a type of radiation that is usually a measurable heat source. IR is one of the broader parts of the EM spectrum. My point is to say, that when you "radiate" some thing with an IR source:
1) You don't know if is also radiating other EM waves unless you know the specs.
2) You're still exciting molecules with that energy even if it isn't causing a seen effect. I highly doubt anything will happen unless you have a very high powered IR source. You should really ever focus high power lasers of any source onto your body, because higher intensities could inflict damage.

To Learn more about IR radiation:
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ask_astronomer/faq/radiation.shtml

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I was aware that it's not a good idea to aim a source or IR directly to the eyes. Sometimes I see in the street CFTV cameras at night and I can clearly see the IR LEDs as red dots, how could this happen as IR is not seen? –  Vladimir Nov 28 '13 at 0:15
    
As I mentioned, You never know if a source is only radiating one wavelength. The red exists because those "IR LEDs" also have radiation that is in the visible spectrum. Red (visible) light is closest to IR radiation in the EM spectrum. See the spectrum here. This only applies for radiation that is being emitted not detected. pion.cz/_sites/pion/upload/images/… –  Sean Nov 28 '13 at 0:19
    
Wait, wait wait wait. Those CFTV camera's have a red light only to let you know that it's recording...The outgoing red light has nothing to do with the light that is being absorbed, aka the IR light. The IR light for the camera is generated from your body, as thermal radiation. –  Sean Nov 28 '13 at 0:21
    
I added a picture of the IR LEDs as I mentioned in the comments to better illustrate the question. The red dots aren't of the LED that indicates that the device is powered on. –  Vladimir Nov 28 '13 at 12:49
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