The Spectronic 20, often called the Spec 20, is a spectrophotometer. A spectrophotometer measures the intensity of a light beam before and after it passes through a sample and compares these two intensities. The Spec 20 reports two types of measurements: percent transmittance and absorbance.
Percent transmittance is the ratio of the intensity of the light passing through the sample to the intensity of the light shining on the sample multiplied by 100%.
Absorbance is the log of the transmittance.
The Spec 20 can measure absorbance and transmittance over a range of wavelenghts.
You must select a wavlength and calibrate the instrument at that wavelength
before making any measurements.
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