actinometry
  光量測定
  ac·ti·nom·e·try /-ˈnɑmətrɪ/ 名詞
  感光測定法,光化線強度測定法
  Ac·ti·nom·e·try n.
  1. The measurement of the force of solar radiation.
  2. The measurement of the chemical or actinic energy of light.
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  actinometry
       n : measuring the intensity of electromagnetic radiation
           (especially of the sun's rays)