See Infrared with a TV Remote | Try it Yourself!

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    Infrared
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Discussion Overview

The discussion revolves around the ability to see infrared (IR) light emitted by TV remote controls, exploring personal experiences, perceptions, and the underlying physics of infrared visibility. Participants share anecdotes, raise questions about the nature of IR light, and discuss the implications of human sensitivity to different wavelengths.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant describes seeing a faint glow from an IR LED on a remote control, suggesting it may be a sub-harmonic frequency, while another counters that it is likely the tail in the near-IR spectrum.
  • There is mention of a previous thread discussing the visibility of IR light, and a participant recounts a conversation with an optoelectronics professor who dismissed the idea that some people can see IR.
  • Concerns are raised about the potential dangers of viewing IR light, as human eyes are not sensitive to it, and it can cause damage in dark conditions.
  • Some participants inquire whether different remotes emit light at varying frequencies and discuss the possibility of seeing red light from certain remotes.
  • A debate arises regarding the definition of visible light, with one participant questioning if seeing IR would classify it as visible light, while others clarify that IR is a specific range of frequencies.
  • Participants discuss the evolutionary aspect of sensitivity to IR and UV light, suggesting that genetic variations may lead to differing sensitivities in the population.
  • One participant shares their experience of testing various remotes and confirms that the standard wavelength of IR LEDs is around 850 nm, while also expressing interest in testing different IR LEDs.
  • Questions are raised about the effect of wearing glasses on the ability to see IR light, with some suggesting that certain coatings on glasses might impact visibility.
  • A participant mentions using a video camera to confirm the visibility of the IR LED, noting that the camera detects it much more effectively than the human eye.

Areas of Agreement / Disagreement

Participants express a range of views on the visibility of IR light, with some asserting that certain individuals can see it while others challenge this notion. The discussion includes multiple competing perspectives on the nature of IR light and its perception, indicating that no consensus has been reached.

Contextual Notes

Some discussions involve assumptions about human sensitivity to different wavelengths and the implications of using various remote controls. There are also references to the potential dangers of viewing IR light, particularly in low-light conditions, without a clear resolution on the safety aspects.

waht
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I went into a dark room with a tv remote control. Then I waited a couple of minutes until my eyes adjusted to the dark. Then I pressed a button on the remote and I could see a very faint flickering brownish glow eminating from the IR LED.

I'm assuming this was just a sub-harmonic frequency generated by the non-linear characteristic of a diode, and it just happened to fall in the border of visible light.

Anyway, this was very neat. You guys can try it.
 
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Not a sub-harmonic -- that would be non-physical for the diode. You're seeing the tail in the near-IR. Pretty cool.
 
There was a thread in General discussion about how to see IR a while ago.
 
After reading the thread about someone's son being able to see infrared light, I mentioned to my optoelectronics professor that some people can actually see a little of the IR spectrum. He looked at me like I was an idiot...lol
 
leright said:
After reading the thread about someone's son being able to see infrared light, I mentioned to my optoelectronics professor that some people can actually see a little of the IR spectrum. He looked at me like I was an idiot...lol
Sounds like a good opportunity to put him in your pocket (if you're so inclined). Take a hard copy plus some of your own work to his next office hours.
 
Playing with IR like that is a bit dangerous because human eyes are not sensitive to it, but it can do lots of damage. Especially when things are otherwise dark (like if you're trying to see IR).

Humans can see in the near UV, but it's usually blocked by the lens which becomes more opaque to UV as you get older. People who have their lens removed because of cateracts can see into the UV, even if they can't focus well. Also, early prosthetic lenses were UV transparent.
 
I can clearly see the light from my remote controle. Do different remotes usually differ a lot in frequency? Maybe I just happen to have one which emitts some red light too...have to try another one.
 
If you can see IR, isn't it then, by definition, visible light?
:)
 
Sometimes I watch radio. But it's in black and white.
 
  • #10
EL said:
I can clearly see the light from my remote controle. Do different remotes usually differ a lot in frequency? Maybe I just happen to have one which emitts some red light too...have to try another one.
Yes. Some emit red light.

It was https://www.physicsforums.com/showthread.php?t=134077"and I had a control on the test. I could not see the light at all, whereas he could see it quite clearly.
 
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  • #11
Euclid said:
If you can see IR, isn't it then, by definition, visible light?
:)
Well, no. I mean, IR is not defined individually by each person. (Does a blind person count the entire spectrum as IR?)
IR is a specific range of freqs, though it is true that it has a "fuzzy border" with visible light.
 
  • #12
NateTG said:
Playing with IR like that is a bit dangerous because human eyes are not sensitive to it, but it can do lots of damage. Especially when things are otherwise dark (like if you're trying to see IR).

I specifically chose a remote control because it's a convenient source of low power infrared radiation, it's probably less than 1 mW power output, and IR is not ionizing like UV. Besides, a daily IR dose from sun is much greater, even when pupils are dilated.

I thought about evolution for a little bit. Since every offspring has a little different genes from parents because of random mutations (to increase the chances for survival) it makes sense that a small subset of population would develop a greater sensitivity to infrared and others to UV.
 
  • #13
DaveC426913 said:
Yes. Some emit red light.

It was https://www.physicsforums.com/showthread.php?t=134077"and I had a control on the test. I could not see the light at all, whereas he could see it quite clearly.


I can confirm it. Your son was right.

If your remote has a brown filter before the LED, than it would be harder to see then glow.

I tried a couple of different remotes that have the LED sticking out and they all glowed with same intensitiy. The standard wavelength of these diode is about 850 nm.

I'm going to try and get a hold of various IR leds with different wavelength and see which one I can see.
 
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  • #14
what said:
If your remote has a brown filter before the LED, than it would be harder to see then glow.
Well yes. But the discrepancy was marked. I looked and looked and looked and looked and saw nothing at all. He made the right call every single time without the slightest hesitation. I clicked and clicked and clicked the button, trying to throw him off, and he might as well have been looking at a flashlight.

what said:
I tried a couple of different remotes that have the LED sticking out and they all glowed with same intensitiy. The standard wavelength of these diode is about 850 nm.
Really? Good to know. I had just assumed that they'd all be different. But you're right, they wouldn't be, would they?
Here's http://en.wikipedia.org/wiki/Image:Control-remote-spectrum.png" that shows it peaks just shy of 950nm.

So, what is the average for humans?

Looks like about 700nm. So my kid can see all the way down to 850?
According to http://www.sjsu.edu/faculty/watkins/eye.htm", he's off the charts!
 
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  • #15
Does it change if you wear glasses? Can you see it?
 
  • #16
DaxInvader said:
Does it change if you wear glasses? Can you see it?
What do glasses have to do with it? It's 6 inches in front of my face!


P.S. Just to prove to myself I wasn't completely insane, I decided to see what my video cam saw. My video cam detects the LED like it's a searchlight!
 
  • #17
Some glasses has some protection layers.. Anti-reflections.. Or other stuff like it.. Its already hard seeing it with a naked eye.. Just asking the question.
 
  • #18
OIC.

No. No effect.
 
  • #19
Thanks then :P
 

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