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Intensity of EM wave
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Average power per area.
I = ½ε₀cE₀²I = ½ε₀cE₀² = cB₀²/2μ₀. It decreases as 1/r² from a point source.
E₀ = 100 V/m: 13 W/m².
Intensity ∝ amplitude squared.
In more detail
The intensity of an electromagnetic wave is the average Poynting vector magnitude, I = ½ c ε0 E0². It determines how much power a given area receives from the wave.
Real-world uses
- Solar panel output is estimated from the intensity of sunlight.
- Radio signal strength is measured as intensity at the receiver.
- Engineers calculate the intensity of sunlight arriving at a solar panel to estimate its power output.
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Frequently asked questions
How is intensity related to amplitude?
Intensity is proportional to the square of the electric field amplitude.
What is the solar constant?
About 1361 W/m² at the top of Earth's atmosphere.
How is intensity related to amplitude?
Intensity is proportional to the square of the electric field amplitude, so doubling the field gives four times the intensity.
Related topics in AC Circuits & EM Waves
Relation between E and B · Energy of EM waves · Poynting vector · Radiation pressure · EM spectrum · Radio waves