Electromagnetic radiation (EMR) threshold

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SUMMARY

The threshold energy or frequency required for an electromagnetic field to transition from near-field to far-field (self-propagating electromagnetic radiation, EMR) is not a fixed constant. Instead, the transition depends on the distance from the source, where both near-field and far-field components coexist. As the distance increases beyond a few wavelengths, the near-field component diminishes rapidly, leaving predominantly far-field characteristics. This understanding clarifies the nature of EMR propagation.

PREREQUISITES
  • Understanding of electromagnetic field theory
  • Knowledge of near-field and far-field concepts
  • Familiarity with wavelength calculations
  • Basic principles of wave propagation
NEXT STEPS
  • Research the mathematical models for near-field and far-field transitions
  • Explore the implications of distance on electromagnetic field strength
  • Study the characteristics of electromagnetic radiation at various frequencies
  • Investigate practical applications of EMR in telecommunications
USEFUL FOR

Physicists, electrical engineers, and anyone involved in the study or application of electromagnetic fields and radiation propagation.

Homestar1
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What is the threshold energy (or frequency) required for an electromagnetic field to transition from a near field to become self propagating (EMR), far field? (If I'm using the right definitions to ask the question correctly). Is this constant or are there other details needed to calculate this?
 
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There is no threshold. Given some distance from the source, some portion of the field will be near-field and some will be far-field, with the near-field falling off extremely rapidly as distance increases. Once the distance is more than a few wavelengths, there is virtually no near-field left.
 
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Ah, that makes sense! Thanks so much!
 

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