(9) Internal Revenue Code means the Internal Revenue Code of 1986 in effect for the federal tax year beginning on January 1, 2007, not including any changes made by federal law after that date, and any regulations adopted under that code applicable to that period.
Absorbance is the negative logarithm of the percent transmittance divided by 100. A spectrophotometer can be set to measure either the percent transmittance or the absorbance of a solution. In lab, you will be using a spectrophotometer called the Spectronic 20 or Spec 20 to measure absorbance.
By recording the attenuation of light for various wavelengths, an absorption spectrum can be obtained. In physics, absorption of electromagnetic radiation is the way in which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed into internal energy of the absorber, for example thermal energy. The reduction in intensity of a light wave propagating through a medium by absorption of a part of its photons is often called attenuation.