Atmospheric Refraction

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Does atmospheric refraction only work at certain temperatures, distances, and shape of the object (i.e. only spheres)?
 

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berkeman
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Thread closed briefly for Moderation...
 
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berkeman
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Thread is re-opened after deleting a questionable reference. We can discuss the science involved in atmospheric refraction in this thread, as long as all references are to mainstream science. Thank you. :smile:
 
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Ok, so cold and warm air are required for this to occur. Can this happen at close distances or is there a limit?
 
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berkeman
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Ok, so cold and warm air are required for this to occur. Can this happen at close distances or is there a limit?
All it takes is light rays traversing a change in the index of refraction at an angle.

I've seen the same effect from light refracting off the hot hood of a car fairly close by. Since it involves angles, the larger the delta-n and the larger the distance, the larger the apparent visual displacement effect, no?
 
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sophiecentaur
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Look over the top of a hot CH radiator at a scene outside. You can often see shimmering due to the varying refraction through the turbulent mix of warm and cooler air. That refraction effect takes place right in front of you and it's more noticeable through binoculars.
 
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jbriggs444
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Ok, so cold and warm air are required for this to occur. Can this happen at close distances or is there a limit?
Which "this" are you talking about? Atmospheric refraction can happen with atmospheric density variations due to altitude even without a temperature difference.

As for distance dependence, a particular temperature/density gradient will result in a particular curvature of light rays. At close range and a small gradient, you won't get much total deflection.
 
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Drakkith
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Ok, so cold and warm air are required for this to occur. Can this happen at close distances or is there a limit?
Temperature isn't directly responsible for the refraction of light through the atmosphere or any other gas. What is needed is a variation in the index of refraction. Hot air is less dense than cooler air, and thus has a lower refractive index. But since density also changes with altitude, the index of refraction of the atmosphere also increases as you get closer to the surface.
 

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