Power in beam of light given amplitude

AI Thread Summary
To calculate the power of a beam of light from the electric field amplitude, one must consider that energy density is proportional to the square of the amplitude. In a vacuum or air, the average energy density can be multiplied by the speed of light to find the power. The magnetic component of the electromagnetic wave contributes to the total power, accounting for about 50%. In a one-dimensional scenario, the power can be expressed in watts per square meter (W/m²), and if the radiation is uniformly emitted, the total power can be obtained by multiplying this value by the surface area of a sphere. Understanding these relationships is crucial for accurate power calculations.
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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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