- #1
vincikai
- 9
- 0
okay, i forgot why is the sky blue again?
What is your current educational level?vincikai said:okay, i forgot why is the sky blue again?
It's blue again because the sun rose this morning.vincikai said:okay, i forgot why is the sky blue again?
Farsight said:The sky is blue because we kind of live at the bottom of a rainbow, only it's an "atmosphere bow".
That's a good link--read it. But the blue sky has nothing to do with us "living at the bottom of a rainbow", whatever that might mean.Farsight said:
Farsight said:Interestingly you can also see the ultra violet.
Nope, you cannot see ultra violet light. However, you have see visible violet light - [itex]\lambda ~ 400nm[/itex].Farsight said:Yep. Look at the photo above.
I zoomed in on the image as close as I can with my browser, and I can't find any yellow pixels below the violet band.Farsight said:Yep. Look at the photo. There's a half-width band of pale translucent yellow under the indigo. With a real rainbow you have to turn your head sideways before you can see it.
Maybe it's more than merely "like" that.Farsight said:It isn't obvious, it's rather like an "after image" colour when you close your eyes after looking at a bright light.
I don't disagree that the photo shows violet light. However, I disagree with the fact that you said it was UV light, UV light is outside the visible spectrum, therefore we cannot see it. We can however, see visible violet light. In addition, I have seen a rainbow with a purple stripe before.Farsight said:Look at the photo Hootenanny. And take a sidelong look at a rainbow next time you see one. It ain't violet.
Exactly. By definition you can't see UV light.Hootenanny said:I don't disagree that the photo shows violet light. However, I disagree with the fact that you said it was UV light, UV light is outside the visible spectrum, therefore we cannot see it. We can however, see visible violet light. In addition, I have seen a rainbow with a purple stripe before.
I know, hurkyl. But have a look again for some yellow pixels. You will find them. That's step one.Interference bows aren't ultraviolet light.
Sure it's beyond the normal colour range Dave, and sure, you can't normally see it. But not by definition.By definition you can't see UV light.
Go to google and type in 'define: UltraViolet light'.Farsight said:Sure it's beyond the normal colour range Dave, and sure, you can't normally see it. But not by definition.
Farsight said:Sure it's beyond the normal colour range Dave, and sure, you can't normally see it. But not by definition.
If you know that interference bows are not ultraviolet light, then why the heck did you bring them up?Farsight said:I know, hurkyl. But have a look again for some yellow pixels. You will find them. That's step one.
You might want to check the definition again. e.g. the first three Google definitions, or the first sentence at Wikipedia.Farsight said:Sure it's beyond the normal colour range Dave, and sure, you can't normally see it. But not by definition.
Farsight said:Zapper: you get your hosepipe out in the bright sunshine, and turn the nozzle to a fairly fine mist, preferably in front of a dark area like an open garage door. You position the spray and yourself so you can see the rainbow you're making. Now you turn your head sideways to look at the rainbow with your peripheral vision. You should be aware of a brightness below the violet band.
All: we all know bees can see UV. And diurnal birds and rats and bats have some degree of UV perception.
http://www.mpih-frankfurt.mpg.de/global/Na/eindex.htm
Farsight said:Zapper: 248nm does sound very short. Have a look at "shortest visible wavelength" and note the "except for a few".
http://www.rattlesnake.com/notions/birds-color-vision.html
Farsight said:It's relevant Zapper, because this is a Physics Forum where we all enjoy , debate, thought, and learning. And statements like:
Ultraviolet light has a wavelength of [itex]100nm < \lambda < 400nm[/itex], the shortest visible wavelength of light our eyes can percieve is 400nm therefore, I repeat again UV light is not visible to the naked eye under any cicumstances
...deserve a response that says there are variations in human visual perception, there is no magical cut-off at precisely 400nm, some people can see further into the ultraviolet than others.
People have a range of capabilities which invalidates a hard-and fast cutoff at 400nm. If you want to find somebody who can definitely see into the UV range just look at aphakia:ZapperZ said:But you're making a speculation here because (i) you haven't shown someone who can actually see in that range and (ii) you were using invalid examples to somehow support your argument that yes, we can see the UV range.