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Thread: How do Antenae pickup electromagnetic waves?

  1. #1 How do Antenae pickup electromagnetic waves? 
    Forum Cosmic Wizard icewendigo's Avatar
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    Hi there

    I was wondering why and how do antena (radio) and retina cells (visible light) pickup the particular em Wavelenghts that they do?


    What does the turning a radio knob translates has (does it alter the antenna or what)?

    Is there any relationship between the antena's size and the lenght of the wavelenght it can pickup? (or transmit?)



    Thanks in advance :-D


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  3. #2  
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    Antennae and retinas work by entirely different principles.

    Radio waves that stike antennae cause electrons to surge back and forth, as determined by the frequency of the EMR. Most of the energy is reflected or reradiated back into space. The antenna is attached to a tuning circuit that lets a few specific wavelengths pass through to the rest of the radio circuitry.

    The tuning devices allow various frequencies to pass through and to block the rest. They typically work by altering the capacitance of a resonant circuit.

    Yes, the antenna's size, configuration, and position have a tremendous effect on its effectiveness at receiving various wavelengths.

    The retinal cells work on a different principle. They use photochemical reactions. Light of the proper frequency alters the chemical structure of the cells' components. The reactions are reversible. The new stuctures, when formed, transmit an impulse along the optic nerve to the brain. The various photochemicals in the eye react only to EMR in the visible spectrum.


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    They use photochemical reactions. Light of the proper frequency alters the chemical structure of the cells' components. The reactions are reversible
    hmm interesting spin off from this, i might be talking a load of rubbish but here it goes.

    If it is a reversible reaction does that mean an equilibrium is set up between the chemically altered structure and the normal structure.

    Therefore if you are continually exposed to a light of certain frequency the amount of chemically altered structure will increase.

    And therefore the equilibrium will shift to try to reverse this by producing more of the normal structure.
    So does that mean the more you are exposed to light the quicker you can revert to normal structure?
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  5. #4  
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    If it is a reversible reaction does that mean an equilibrium is set up between the chemically altered structure and the normal structure.
    Yes, this is true.

    Therefore if you are continually exposed to a light of certain frequency the amount of chemically altered structure will increase.
    We are talking about rhodopsin, a compound found only in the rods and cones of the eye's retinas. There are only so many molecules of rhodopsin; when each is converted to its isomeric form there will be no further increase.

    In practice, the eye is constantly shifting its position. Rhodopsin quickly converts from one form to another as the eye forms and re-forms its various images.

    For a bit more information, see here: http://ebiomedia.com/gall/eyes/Images.html

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  6. #5  
    Forum Cosmic Wizard icewendigo's Avatar
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    Thanks SteveF! :-D
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  7. #6  
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    You are quite welcome.

    Any time.
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    Q: I heard somewhere that our pupils are black because they are absorbing all of the light that goes into them, is this true?
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

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    Forum Bachelors Degree Shaderwolf's Avatar
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    It's shadows I thought. If you flash a picture, red-eye is actualy people looking into the back of your eye
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  10. #9  
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    Thats creepy!
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

    -Einstein

    http://boinc.berkeley.edu/download.php

    Use your computing strength for science!
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