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Old May 11th 2008, 10:56 AM   #1
Air
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Refraction

Q: A three-year-old child at a barbecue was heard to remark: “The trees look like jelly – they’re all wobbly”. She was looking at the trees over the top of the hot barbecue. Heated, less dense air was rising from the barbecue in uneven layers, changing the direction of the light from the trees in a varying pattern.

The diagram shows a ray of light from the trunk of each tree reaching the child before the barbecue is lit.


After the barbecue is lit, a layer of hotter, less dense air is between the child and the trees. Complete the diagram below to show a ray of light from each of the trees A, B and C reaching the child. The ray A has been started for you.


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My Problem: This is one of the question that I do not understand. I understand that in hot material, the ray moves away from the normal but I don't know how to draw it on this diagram. Can someone complete the diagram? Thanks in advance.
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Old May 11th 2008, 07:43 PM   #2
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Originally Posted by Air View Post
Q: A three-year-old child at a barbecue was heard to remark: “The trees look like jelly – they’re all wobbly”. She was looking at the trees over the top of the hot barbecue. Heated, less dense air was rising from the barbecue in uneven layers, changing the direction of the light from the trees in a varying pattern.

The diagram shows a ray of light from the trunk of each tree reaching the child before the barbecue is lit.


After the barbecue is lit, a layer of hotter, less dense air is between the child and the trees. Complete the diagram below to show a ray of light from each of the trees A, B and C reaching the child. The ray A has been started for you.


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My Problem: This is one of the question that I do not understand. I understand that in hot material, the ray moves away from the normal but I don't know how to draw it on this diagram. Can someone complete the diagram? Thanks in advance.
When a ray of light enters a region where the material is less optically dense than the original the, as you say, the refracted beam has a larger angle from the normal. So this is going to imply that the rays from A and C are going to cross before reaching the child. The ray from B obviously does not get deflected at all and goes straight through.

-Dan
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Old May 12th 2008, 09:04 AM   #3
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Originally Posted by topsquark View Post
When a ray of light enters a region where the material is less optically dense than the original the, as you say, the refracted beam has a larger angle from the normal. So this is going to imply that the rays from A and C are going to cross before reaching the child. The ray from B obviously does not get deflected at all and goes straight through.

-Dan
Can you complete the diagram so I can see how it is please?
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Old May 13th 2008, 05:12 AM   #4
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I'm not sure what you are still confused about? Here is part of the diagram.

The ray from A will be bent more than before so it will appear to the right of the observer. The ray from B was never deflected, so it will appear in the same place as before. You do the ray for C.

-Dan
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Refraction-ray2.jpg  
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