Detecting visible light EM radiation with an antenna

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Discussion Overview

The discussion revolves around the feasibility of detecting visible light electromagnetic radiation using an antenna-like structure, similar to those used for radio waves. Participants explore the theoretical and practical aspects of constructing such antennas, including size considerations and the nature of light detection.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that it is possible to construct a radio-like antenna to detect visible light, similar to antennas used for radio waves.
  • Others argue that the antenna would need to be extremely small, on the order of the wavelength of visible light, which is in the hundreds of nanometers.
  • A participant questions whether "really tiny" refers to the size of photoreceptors in the retina, suggesting a comparison to the size of molecules involved in light detection.
  • It is noted that while photoreceptors are not classical antennas, their active molecules are smaller than the wavelength of visible light, which may be relevant for detection efficiency.
  • Another participant clarifies that the absorption of a photon by a molecule leads to a change in shape, which can trigger a neural signal, but this process does not involve the detailed detection of light characteristics.

Areas of Agreement / Disagreement

Participants generally agree on the need for very small antennas to detect visible light, but there is no consensus on the specifics of how detection would work or the comparison to biological systems like photoreceptors.

Contextual Notes

The discussion includes assumptions about the size and function of antennas and photoreceptors, as well as the limitations of current electronics in detecting rapidly oscillating electric fields.

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If visible light is part of the EM spectrum just like radio waves, is it possible to construct a radio like antenna (metal pronged structure) to detect them?
 
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Actually yes, but the antenna needs to be REALLY REALLY tiny.

http://en.wikipedia.org/wiki/Nantenna

The main problem is that the electric field oscillates so quickly that current electronics cannot operate fast enough to directly record the field.
 
Drakkith said:
Actually yes, but the antenna needs to be REALLY REALLY tiny.

By REALLY REALLY tiny, do you mean about the size of the photo receptors in our retina's?
 
About the size of the wavelength, some hundred nanometers (about 0.0000005 meters)
Our photo receptors are not classical antennas, and their active molecules are even smaller than the wavelength.
 
MikeGomez said:
By REALLY REALLY tiny, do you mean about the size of the photo receptors in our retina's?

From the wiki article I linked:

The wavelengths in the solar spectrum range from approximately 0.3-2.0 μm.[3] Thus, in order for a rectifying antenna to be an efficient electromagnetic collector in the solar spectrum, it needs to be on the order of hundreds of nm in size.

I don't know how large the molecules in our eyes are that actually detect the light, so I can't give you a comparison. The cells themselves are much larger than the wavelength, but only the molecule size matters I believe. Still, they aren't even antennas. They just absorb EM energy and change shape without determining any details about the light other than "Hey, I got a photon!".
 
That's right... see here

Ultimately, the absorption of a photon causes a bent molecule to straighten out. If this happens enough times within a short period and a very localized region (spatial/temporal summation), the net activity is enough to depolarize a membrane to originate a neural signal.
 

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