Quote:
Originally Posted by Donger
I would imagine that red goes farther, with its longer wavelength.
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It would appear that you are correctomundo.
http://http://www.visualillusion.net/Chap15/Page03.php
Before the war began, a Brazilian battleship launched in this country was provided with a system of blue lights for use when near the enemy at night. Blue was adopted doubtless for its low range compared with light of other colors. We know that the setting sun is red because the atmospheric dust, smoke, and moisture have scattered and absorbed the blue and green rays more than the red and yellow rays. In other words the penetrating power of the red and yellow is greater than that of the blue rays. This country made use of this expedient to some extent. Of course, all other lights were extinguished and portholes were closed in ocean travel during the submarine menace.
http://http://www.worsleyschool.net/...cattering.html
The questions about blue light first arose when we were looking at how to demonstrate that white light is made up of different colours, using glow tubes.
We had previously noticed that the blue Christmas lights on our home, while nice and bright in the yard, were invisible from the road. The question we asked was 'Why does blue light seem to fade out with distance, while red and yellow don't?'
The answer has to do with air ... the molecules that light must pass through to get to your eye. In order to explain what happens to the light, you'll need to remember that ordinary white light contains all the colours of the spectrum.
The fact that white light is made up of all the colours of the rainbow was demonstrated by Isaac Newton using a prism. White light passed into the prism came out in a spectrum, because the glass caused the different colours to slow down by different amounts, changing their angles of exit. This phenomenon is called refraction.
As white light from the sun enters our atmosphere, it must pass through this gas, which is composed mostly of nitrogen and oxygen molecules, before it can reach the surface. As it passes through, each of the different colours in the light interact with the air molecules.
A simple way to describe what happens would be to say that the air molecules, which are about 0.0004 millimeters in diameter, are very close in size to the waves of blue light. Other colours have bigger or smaller waves, and mostly pass right through, but the blue light waves hit the air molecules and scatter in all directions. As the sunlight comes down through the atmosphere, the blue light in it gets scattered all over the place. Some of this scattered light (there's a lot of it) reaches our eyes, making the sky seem blue. The sunlight that's left that finally reaches the ground has lost most of its blue light, leaving it yellowish in colour, so the sun itself appears yellow.
In space, there is no air to scatter the different colours in light, so the sun would look white and the 'sky' would be black.
This also explains why blue lights get dimmer with distance. If you're far enough away from the blue Christmas lights decorating your house, much of the blue light from them gets scattered every which way, and there wasn't very much of it to start with, so very little of it gets to your eye. You can't see the bulbs.