Solar Radiation

Cosine Law and Surface Incidence

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Surface incidence is governed by the Lambert cosine law. This states that the relative intensity of radiation or light on a surface is equal to the cosine of the angle of incidence, and that the relative area over which it is distributed is the inverse of this value. This applet provides an interactive and highly visual demonstration of this effect on both horizontal and vertical surfaces. You can interactively drag altitude and azimuth angles to see changes in both the distribution area and relative intensity of an incident energy beam. It is particularly interesting to see these effects simultaneously on both surfaces.