Power in beam of light given amplitude

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Discussion Overview

The discussion revolves around calculating the power of a beam of light based on the electric field amplitude provided in a one-dimensional scenario. Participants explore the relationship between electric field amplitude, energy density, and power, particularly in the context of a vacuum or air.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Mathematical reasoning

Main Points Raised

  • One participant seeks to calculate the power of a light beam given the electric field amplitude values along a specified line.
  • Another participant notes that energy density is proportional to the squared amplitude and mentions that power can be derived from average energy density multiplied by the speed of light, while also highlighting the importance of the magnetic component.
  • A participant expresses uncertainty about obtaining a specific power value in watts and acknowledges the need for the magnetic field component (H) in their calculations.
  • Another participant clarifies that the result will be in W/m² and suggests that if the radiation is uniformly emitted, the total power can be calculated by multiplying the intensity by the surface area of a sphere.

Areas of Agreement / Disagreement

Participants generally agree on the relationship between electric field amplitude and power but do not reach a consensus on how to apply these concepts specifically in the one-dimensional scenario presented.

Contextual Notes

There are unresolved aspects regarding the integration of the magnetic field component and the specific calculations needed to derive total power from the given amplitude data.

Who May Find This Useful

This discussion may be useful for individuals interested in the physics of light, electromagnetic theory, or those looking to understand the relationship between electric fields and power in light beams.

Cspeed
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I would like to calculate the power of a beam of light once I know the electric field amplitude. For example if I know the amplitude along a line from -1 meter to +1 meter every 0.5 m is [1, 2, 2.5, 2, 1 V/m], how can I find the power from this is? Is there enough info? (it's in vacuum/air) Thank you.
 
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Energy density is proportional to the squared amplitude (see Wikipedia for example), and power is just average energy density times the speed of light. Don't forget the magnetic component, which is 50% of the total power.
 
Thanks, but I'm not sure still. I knew that power was proportional to the square of amplitude, but I'm hoping to get a figure in watts. I see that I need H as well. But how does this all fit into my 1-D scenario?
 
You get W/m^2 - what else did you expect? If the source emits radiation uniform in space, you can multiply that with the corresponding sphere surface area to get the total power.
 

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