Earth Science [Easy] Why is the sky blue? (Prisms)

Discussion in 'Earth Science' started by pineappleupsidedown, Dec 24, 2004.

  1. pineappleupsidedown

    pineappleupsidedown Premium Member

    What you need:
    [*]a clear, straight-sided drinking glass, or clear plastic or glass jar
    [*]water, milk, measuring spoons, flashlight
    [*]a darkened room

    What to do:
    [*]Fill the glass or jar about 2/3 full of water (about 8 - 12 oz. or 250 - 400 ml)
    [*]Add 1/2 to 1 teaspoon (2 - 5 ml) milk and stir.
    [*]Take the glass and flashlight into a darkened room.
    Hold the flashlight above the surface of the water and observe the water in the glass from the side. It should have a slight bluish tint.

    Now, hold the flashlight to the side of the glass and look through the water directly at the light. The water should have a slightly reddish tint.
    Put the flashlight under the glass and look down into the water from the top. It should have a deeper reddish tint.

    What happened:
    The small particles of milk suspended in the water scattered the light from the flashlight, like the dust particles and molecules in the air scatter sunlight. When the light shines in the top of the glass, the water looks blue because you see blue light scattered to the side. When you look through the water directly at the light, it appears red because some of the blue was removed by scattering.

    This is why the sky looks blue during the day, but when the sun is setting, the sky looks red.

    ---Pineapple
     
  2. Mizar

    Mizar Premium Member

    If there was more pollution( more particles) in your sky would the sky appear darker red at sun set?

    Someone once told me this and I have always thought it false but never looked into it.
     
  3. bodebliss

    bodebliss The Zoc-La of Kromm-B Premium Member

    I once heard a much more technical explanation for why the color is the shade of blue it is involving the absorption and reradiation of different wavelengths of light and oxygen which leave blue as the predominate color.

    Bode
     
  4. JcMinJapan

    JcMinJapan Premium Member

    The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.

    However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.

    As you look closer to the horizon, the sky appears much paler in color. To reach you, the scattered blue light must pass through more air. Some of it gets scattered away again in other directions. Less blue light reaches your eyes. The color of the sky near the horizon appears paler or white.

    http://www.sciencemadesimple.com/sky_blue.html
     
  5. bodebliss

    bodebliss The Zoc-La of Kromm-B Premium Member

    JCM,
    That's It! That is the explanation I was looking for.
     
  6. tablet

    tablet Premium Member

    Beside the sky being blue. Who here study sky/cloud and the horizon? I'm always fascinated by the colour and mood it creates. From haze to how light are being scattered, from sunrise to sunset and all the colours. IF any of you come across good site on the whole thing about SKY and what happens from morning to night, please pass along.
     
  7. /Future Corpse/

    /Future Corpse/ Premium Member

    The sky is not blue in an absolute sense. It is only seems blue because of the way that the human eye interprets external information.
     
  8. tablet

    tablet Premium Member

    Click here for photo on Sky/Sunrise/Sunset ect...


    Blue Sky - Red Sunset
    6.gif
    Interesting, just by looking at this image you know that at Sunset (horizon) the sun have to go through more air (atmosphere) than at Noon. (The image is gif and it has transparency, looks like it doesnt' look too well on a black background. So just select the image or visit the site)

    --------------------
    BY the way, I have a question. You know one of those beam that shoot out light? Red for example. How do they do it? The wavelength for red is about 650 nanometers (the longest in the 'visible light' spectrum) and the shortest is Blue which is about 47m nm. Any colour that is Bluer than Blue cannot be seen.

    So back to the question. IF They were to create a beam that shoot out red light, what's the trick?