SINCE 1828
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cosine law

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Definition of cosine law

: either of two laws of radiation:
a : the radiant flux emitted in a given direction from a given small area of a perfectly diffusing surface varies as the cosine of the angle of emission
b : the irradiation by parallel rays falling on a surface varies as the cosine of the angle of incidence

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“Cosine law.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cosine%20law. Accessed 22 Jan. 2021.

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