3. Summary comparison of emissions from sources to LE

3.1 Solar irradiance

Let's start with the sun, even though the sun is not an artificial form of radiation. Solar radiation is modeled by a black body at 5,800 K with an emission maximum at 520 nm, half of which is in the visible, the other half in the IR (25% of radiation is below 520 nm and 75% above, part of which is in the IR with V (λ) ≈ 0). UV represents around 1% of radiation. Solar irradiance at the earth's surface is around 1 kW · m ^–2 (depending on surface location, atmospheric transparency, clouds...). This corresponds to a visual illuminance of around 10 ⁵ lx. The total power emitted by the sun is 4 × 10 ²⁶ W.

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