What is the magnitude of the Electric field inside a light wave?

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Discussion Overview

The discussion revolves around the magnitude of the electric field inside a light wave, with a focus on understanding the values associated with different light sources, such as computer screens and sunlight. Participants explore the relationship between electric field strength and light intensity, touching on both classical and practical aspects of electromagnetic waves.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant seeks an intuitive understanding of the electric field magnitude associated with light from a computer screen, questioning whether it is on the order of 10^6 N/C or 10^-6 N/C.
  • Another participant references a value derived from a textbook, stating that an intensity of 1300 W/m^2 corresponds to approximately 1000 N/C.
  • A different participant suggests that the quoted intensity may pertain to sunlight at a distance of 1 AU, expressing uncertainty about whether this includes the entire electromagnetic spectrum or just specific types of light.
  • One participant notes that the electric field can vary significantly, citing that a laser beam can produce a much stronger electric field capable of ionizing air, while light from a star has a weaker electric field. They also mention the relationship between electric field amplitude and light intensity, providing a range of intensities from 10^-14 W/m^2 to 10^12 W/m^2.

Areas of Agreement / Disagreement

Participants express varying views on the magnitude of the electric field in different contexts, indicating that there is no consensus on a specific value or range. The discussion remains unresolved regarding the exact relationship between electric field strength and light intensity across different sources.

Contextual Notes

Participants highlight the dependence of electric field strength on the intensity of light, but do not resolve the assumptions or definitions related to the measurements of intensity and electric field strength.

silverdiesel
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I know the magnitude varys a lot, but I am just looking for some basic intuitive idea of light. Is the magnitude of light from my computer screen on the order of 10^6 N/C or more like 10^-6 N/C?
 
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Nevermind, I finally found it in my gen phys 2 book derived from the Intensity. 1300 W/m^2 ~ 1000 N/C
 
I think the figure you quoted is the value for the intensity of light from the sun at a distance of 1 AU. But I'm not sure if that includes the entire EM spectrum, or just heat and visible light.
 
Classically at least, the field can vary widely, a laser beam for example might have a huge E field (enough to induce air to ionise in some cases). The light from a star obviously has a much weaker E field. Note that the amplitude of the E field is related to the intensity of a light beam. To give you an idea in terms of numbers (in intensity), we can detect 10^-14 W/m^2 and produce 10^12 W/m^2 (as a conservative estimate), that's 26 orders of magnitude right there.

Claude.
 
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