Extinction Index K: Expression & Calculations

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Discussion Overview

The discussion centers on the concept of the extinction index (K) in the context of a monochromatic plane wave propagating through a medium. Participants explore the relationship between the wave's frequency, the medium's resonance frequency, and the attenuation of the electric field over a specified distance.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant presents a scenario involving a monochromatic plane wave with a specific frequency and resonance frequency, noting that the electric field decreases significantly over a distance of 1 cm.
  • Another participant inquires about the meaning of the extinction index and seeks an equation that describes the amplitude decrease of the wave with distance.
  • A different participant defines the extinction index as the imaginary part of the refractive index and connects it to wave attenuation, mentioning the expression for electric fields in relation to complex wave vectors.
  • Further, a participant asks which part of the complex wave vector equation describes the wave's attenuation, suggesting that providing the actual equation would be more beneficial than a verbal description.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the extinction index and its implications, with some seeking clarification while others provide definitions and context. The discussion remains unresolved as participants explore different aspects of the topic without reaching consensus.

Contextual Notes

Participants have not yet provided a complete mathematical expression for the extinction index or fully addressed the implications of the given data regarding the electric field's attenuation.

Carmen_8
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We have a monochromatic plane wave with a frequency ω=10^15 (1/s). It is spread in a medium whose resonance frecuency is also ω=10^15 (1/s). The wave is attenuated in the spreading direction. In 1 cm, the electric field of the wave is 10 times smaller. Give an expression for the extinction index (K) (imaginary part of refractive index).

I know the expression for K(ω) in the special case that the wave's frequency is equal to the medium's resonance frequency. The problem is that I don't know what to do with the other data: 'In 1cm, the electric field of the wave is 10 times smaller'.
 
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What is the meaning of the extinction index? What equation do you know that describes how the amplitude of the wave decreases with distance from source?
 
nasu said:
What is the meaning of the extinction index? What equation do you know that describes how the amplitude of the wave decreases with distance from source?
The extinction index is the imaginary part of refraction index. The physical meaning has to do with the amount of attenuation of the wave. And the answer for the second question..the only one that I have in mind is the expresion for electric field as a monochromatic plane wave with a complex wave vector.
 
OK, and which part of the equation of the plane wave with complex wave-vector describes the attenuation of the wave?
It will be more useful to write the actual equation rather than describing it in words.
 

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