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Light from an antenna

  1. Jul 24, 2003 #1
    If light is just an EM phenomena like radio waves (with more energy) would it be possible to build a transmitter that transmits in the light range? If you were to do this, would you see light that just seems to propagating from the antenna?
  2. jcsd
  3. Jul 24, 2003 #2


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    If you could see in radio light, you'd look up at an antenna and see an odd fuzzy, pulsing light.

    Radio waves do not behave like optical light however, due to their longer wavelength -- radio waves bend around things, diffract through large openings, and generally don't behave in the straight-line fashion you're used to light behaving in. It would be weird indeed to have radio eyes.

    To answer your question, it is impossible to build a normal radio transmission antenna that can produce light frequencies. The technique of jiggling electrons in a wire (an antenna) becomes very inefficient in the microwave region. People use different technologies to generate each of microwaves, light, ultraviolet, x-ray, and gamma radiation. No one technology can produce them all. (Not yet, anyway.)

    - Warren
  4. Jul 24, 2003 #3
    Somewhere I read:
    "The antenna for light is called an atom".
  5. Jul 24, 2003 #4
    It's called a light bulb.

  6. Jul 24, 2003 #5
    Nonono - radiation must be coherent from an antenna

    Plus it must work 2-way. Ever seen a lightbulb convert light into electricity?
    Last edited: Jul 24, 2003
  7. Jul 25, 2003 #6
    Well no, but it can via the Photoelectric effect. The filament coil won't be as efficient as a large plate but it should work. But here's the interesting part - I think antennas are said to be reciprocal devices.

    An antenna good for 1 meter wavelenght is good for both transmission and reception. The light bulb clearly won't be. Is this related to coherence as an assumption in a working antenna?
  8. Jul 25, 2003 #7
    anybody heard of laser-diodes? The ones used in CD-players.....
  9. Jul 25, 2003 #8
    Yes. Antenna theory has to do with the Fourier-transform of the e.m. field. You can transform only pure (coherent) states, not mixed states.
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