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Thread: radiation shield / coherence

  1. #1 radiation shield / coherence 
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    I need help with a science fair project.

    I will tell u briefly what i am trying to do. In a Science Fair, i need to prove
    that sound, radio, and light waves can be affected by destructive interference.
    I already have used my computer to lower the dB of a given sound wave by about
    85%. I have taken one speaker from the computer and angled it about 10 degrees
    toward the other, and let one speaker play the opposite continuous tone as the
    other (at 350Hz). This works fine. Radio and light waves are much more difficult to do a demonstration for, so i hope that i can JUST prove the possibility of canceling them out using just math. I read that light waves are known to spike randomly quite a bit, so it will be difficult in a real life situation to use a computer to cancel them. I also wanted to suggest to people that this may be practical when used as a shield or dampening field for radiation.

    My question is, can someone help me prove mathematically that destructive interference works with radio waves and light waves?

    and does anyone have any suggestions to make the project more interesting to judges

    thank you for your time everyone


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  3. #2  
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    Showing the destructive interference of light is remarkably easy -- perhaps so easy you might not want to consider it for your project because of its simplicity. Check out destructive interference by an oil slick on water. Here is a basic reference:

    http://nsdl.exploratorium.edu/nsdl/s...age=10&index=0

    The math is also easy.
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  4. #3  
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    It is also easy to create destructive interference of radio waves. The problem is the demonstration, as radio waves are not visible. What you will do is set up standing waves in Lecher transmission lines. Here is your link:

    http://intuitor.com/resonance/standingEwaveDemo.html

    Happy hunting.
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  5. #4  
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    Using interference for a radiation shield would be a pretty tall order. If you are dealing with decay of radioactive material, that occurs randomly, not in a continuous beam of radiation. Also, if you could produce an interference minimum by destructive interference, there will also be a maximum nearby where there is constructive interference.
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  6. #5  
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    yes i understand this, and i was trying to make this an idea for people to think about, but first i need to prove it is possible to cancel at least a radio wave, so does anyone know of a set of equations to show this?

    im just not sure how to go about doing the math, sorry... and i know that it is very difficult to use destructive interference on something that is random. so lets assume that the radio wave is constant, and aprox. around 575,000 Hz
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  7. #6  
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    The math for the interference of light is incredibly simple. See here http://sol.sci.uop.edu/~jfalward/lig...erference.html for example.

    Interference of radio waves? Well, considering that both light and radio waves are electromagnetic radiation, the math is (ta-da!) exactly the same!
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  8. #7  
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    i demonstrated light waves canceling eachother when opposite, and sound waves with high efficiency, but apparently the judges didnt like the project because it was to "original" and "not useful enough for modern society"
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