Primary standard of light

  title={Primary standard of light},
  author={Charles Proteus Steinmetz},
  journal={Transactions of the American Institute of Electrical Engineers},
Light is not a physical quantity, but a physiological effect, that of certain wave-lengths of radiation, and therefore can not be expressed in absolute physical units; it must be measured by comparison with an arbitrarily chosen standard of physiological effect. As a result thereof, even with the best existing primary standard of light, the amylacetate lamp… CONTINUE READING