by Chris Peterson » Sat Apr 09, 2016 6:39 am
GeeBee wrote:The reason a green flash is rare is not that green light is short wavelength. It's kind of mid-range in the visible spectrum in fact. It's that the range of wavelengths the eye/brain perceives as green is pretty narrow compared to the reds/oranges/yellows on the long wavelength side and the blues/violets on the short side. So whatever atmospheric phenomenon produces the flash has to scroll through that very narrow range very slowly in order for us to pick it up as green, just as we never see a green sky, only a blue or red.
The green flash is not particularly rare. The caption used "elusive", which is a good word given that the flash is brief. But if you're on the lookout, you can see it quite frequently.
The wavelengths aren't "scrolled through". The green flash is caused by dispersion, which causes the atmosphere to act like a prism. We barely notice the wavelengths longer than green, because they blend with the orange Sun. We don't see the shorter wavelengths because they are scattered by the atmosphere (the same reason the sky is blue). But there is a
blue flash phenomenon. It has the same cause, but the atmospheric conditions that create it are unusual. So it's not just elusive, but truly rare.
[quote="GeeBee"]The reason a green flash is rare is not that green light is short wavelength. It's kind of mid-range in the visible spectrum in fact. It's that the range of wavelengths the eye/brain perceives as green is pretty narrow compared to the reds/oranges/yellows on the long wavelength side and the blues/violets on the short side. So whatever atmospheric phenomenon produces the flash has to scroll through that very narrow range very slowly in order for us to pick it up as green, just as we never see a green sky, only a blue or red.[/quote]
The green flash is not particularly rare. The caption used "elusive", which is a good word given that the flash is brief. But if you're on the lookout, you can see it quite frequently.
The wavelengths aren't "scrolled through". The green flash is caused by dispersion, which causes the atmosphere to act like a prism. We barely notice the wavelengths longer than green, because they blend with the orange Sun. We don't see the shorter wavelengths because they are scattered by the atmosphere (the same reason the sky is blue). But there is a [url=http://apod.nasa.gov/apod/ap020109.html]blue flash[/url] phenomenon. It has the same cause, but the atmospheric conditions that create it are unusual. So it's not just elusive, but truly rare.