Re:The Difference Between ‘Violet’ and ‘Purple’ (2015)
by blincoln on Tuesday April 02, 2019 @02:01PM
(#19556896)
Let's assume you're correct, and that the more-or-less logarithmic aspect to human vision is inconsequential here, and also that the hump in absorption around 410nm by the red cones is also irrelevant. How would you explain the human perception of violet light as a purple colour, then?
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Re:The Difference Between ‘Violet’ and ‘Purple’ (2015)
by jacobolus on Tuesday April 02, 2019 @02:23PM
(#19557090)
By “violet light” you mean a 400 nm laser or something? Or a blacklight? https://en.wikipedia.org/wiki/Blacklight
In normal circumstances (say, daylight surroundings), a moderate amount of light at very short wavelengths won’t look like much of anything at all, bluish–black, because the cone cells (especially L and M cones which determine red–green response) will be getting much more stimulus from other wavelengths.
If you go to a completely dark room, let your eyes adapt, and look at a blacklight, then you are right that you are at that point going to see it looking purplish because the L cones are stimulated a bit more than the M cones for those wavelengths, and other wavelengths are entirely absent. But this is a really weird edge case for vision.
Re:The Difference Between ‘Violet’ and ‘Purple’ (2015)
by Bendingo on Tuesday April 02, 2019 @11:04PM
(#19560427)
The first sentence in the wikipedia article says:
"A blacklight [...] emits long-wave (UV-A) ultraviolet light [...]."
Why does it say "long-wave" when UV is short-wavelength ?
Re:The Difference Between ‘Violet’ and ‘Purple’ (2015)
by OscarCunningham on Wednesday April 03, 2019 @01:51AM
(#19561082)
Because the light that blacklights emit is on the longer end of the possible UV wavelengths. This is what the UV-A means. There are also UV-B and UV-C with shorter wavelengths.