My wife claims to have trouble seeing colors, though I don’t think she is color blind. As far as I know there is no history of colorblindness in her family. However, at one time I saw her pick out the UV line on a hydrogen spectrum. I don’t remember the wavelength but I think it was the first Lyman series UV line (electron drops from second to first energy level?)
First, is this possibly true? can she really see this line? Second, How common is it for someone to be able to see this part of the color spectrum? Third, what are the likelyhoods that this ability is messing up her vision for other colors (being as what we see as a color is not “contaminated” with a confounding UV aspect)?
Lyman alpha is down at 121.5 nm. Water and peptide bonds both absorb strongly down there, so if your wife picked out the line she must have been seeing fluoresence, rather than the line itself.
When I was in college and taking the first of the three part chemistry class, I discovered that myself and two others in our class could see this line. The Professor had lectured that occasionally a rare few can see this UV hydrogen line, but in years no one in class had seen it. The proof of course was pointing out where the line was, and the fact we could see 4 lines (the UV being the fourth people cant normally see).
On another note, I have a caming add-on for my pc that uses IR led’s, which they say you can barely see in a dim or dark room, yet I can clearly see in my well lit room.
Im not sure about the colors washing out, I dont experience that at all, at least as far as I am aware.
This could be an explanation; I don’t know how I could control for that. Whatever the line may be projected against (paper, plastic) could be fluorescing.
I seriously doubt that you can see 121 nm. That’s down in the vacuum UV, and the air molecules will , be absorbing it. Good thing, too. Those photons are very energetic, and will cause cancers and mutations.
The waty they can tell that bees and other insects can see UV light is to use it to illuminate a non-fluorescing object, and screen all other wavelerngths so that only the desired one falls on the object. You might want to try this with longer-wave UV light. You wouldn’t want to do it with shortwave UV, even if she can see it, because of the danger of exposure (Looking at the 254 nm line from a quartz-envelope mercury lamp can cause “blisters” on the cornea that reportedly feel like grains of sand under the eyelid. It’s like a sunburn on your eyeball, and eventually heals) So keep it longer than 300 nm. You can use one of those “blacklite” bulbs they sell in Spencer’s Gifts, and use a shortpass filter (obtainable from Edmunds, or other optics company) to block the visible lines. Or use a diffraction grating to split the incoming light, and see if she sees lines that you can’t. Normal human vision cuts out before 300 nm, but there’s bound to be variations on the range viible to different people, and your wife might be more sensitive on the short wavelength side than you are.
Fluorescence could also occur at the surface of the eye, within the lens, or in the aqueous humor. Maybe those who can see the line also have a diet that is rich in beets, carrots or vitamin C. Vitamin C is involved in protecting the eye from UV damage.
Yes – as I state above, bees (and, I’m pretty sure, some other insects) have the ability to see further into the UV than people do, and they tested this by illuminating targets (sources of sugar water, IIRC) that bees would go for with various wavelengths of light.
As for what color ir is, I’m guessing that anything down that end will be some sort of bluish-violet, just as people who see wavelengths verging on the infrared descrive it as deep, ruddy red.
A decent, nitrogen flushed, spectrophotometer will get you down to 150 nm. Still, if the source is bright enough, like a carbon arc, and you’re close enough to it, you might get some 121 nm light impinging on the eyeball.
Before replacement lenses for cataract patients were made to block UV rays, it was fairly common for people to be able to see UV after their cataracts were removed - the eye’s natural crystalline lens is a UV blocker. It’s been speculated that Monet’s unearthly use of color was due to this.
There are four hydrogen lines that are visible to humans: 655 nm, 485 nm, 430 nm, 410 nm. You are most likely talking about the 410 nm line that many people have difficulty seeing. These lines correspond to the Balmer series (n[sub]f[/sub] = 2) not the Lyman series.
Oh, yes – one other thing. Unless your spectrophotometer contains all reflective optics, or has been specially constructed for Vacuum UV, this isn’t true. Even Fused silica won’t transmit down that far. You need optics made of Calcium Fluoride or Lithium Fluoride or some other unusual material with high UV transmission, and most of the others are hygroscopic salts.
Yes, I’m not disputing that. It’s just that the upper end of vacuum UV isn’t quite so hard to get in an atmosphere as the name implies, and beam intensity can compensate for a little atmospheric murk.
Yes, as I said, a decent spectrophotometer.
Of course it turns out we’re probably talking about the 410nm line. Up there, you can use dispo plastic cuvettes, and neither protein nor water absorb much.
410 nm isn’t far from the maximal sensitivity of blue cones at 419 nm , so there’s probably no need to invoke fluoresence, merely some people having more blue sensitive cells than others.
I don’t understand this, quite. As this Wikipedia article states, cataract surgery didn’t involve *replacing * the original lens until the 1940s–and Monet had his cataract surgery in 1923. So he would have still had his original lens, right? With its original UV-blocking powers?
James T Fulton claims that peoples’ retinas can pick up ultraviolet; it’s the lens that blocks the UV. But even he says that the UV sensitivity drops off at wavelengths shorter than 300 nanometres.
Is it possible that people with cataract surgery before the 1940s had no lenses in their eyes, and wore special glasses? (Would that even be possible?) What if Monet’s remaining de-cataracted natural lens was a lot thinner, and he could see some more UV, but he still needed glasses to provide the other part of the needed correction?
