Photometry, laws

Laws of Photometry. The time rate at which energy is transported in a beam of radiant energy is denoted by the symbol To for the incident beam, and by P for the quantity remaining unabsorbed after passage through a sample or container. The ratio of radiant power transmitted by the sample to the radiant power incident on the sample is the transmittance T ... 

A. Theory In fact, two fundamental laws actually govern the practice of colorimeteric assays of photometry. 

Beer, a nineteenth-century German physicist, gave his name to a law that allows the calculation of the quantity of light transmitted through a defined thickness of a compound in solution in a non-absorbing matrix. His work is often associated with that of the French mathematician Lambert, who laid down the basis for photometry in the eighteenth century. The result is Beer—Lambert s law, shown here in its current form ... 

The Lambert-Beer law was applied for the determination of the mixing performance, the local concentration c being measured by photometry via the relation... 

Aerosol particle optical thickness (AOT) Sun photometry Beer s law using sun as light source -h... 

Visual spectroscopy can also be semiquantitative. A simple example is the assessment of swimming pool water quality and its chemical content using well-known color reactions and simple sets of colored concentration reference standards. This evaluation of light or color intensity is called photometry. Visual photometry saw one early use in criminal law with the evaluation of breath alcohol concentrations. The test was based on the ability of breath alcohol to chemically reduce the colored chromate ion to a colorless form in aqueous solutions. As more alcohol vapor was bubbled through a chromate solution it became more bleached. The resulting solution was then visually compared to a calibrated, standard set of diluted chromate solutions to determine the subject s breath alcohol content. The test was soon modified to include instrumental measurement of the decolorizing reaction and is referred to as a form of spectrophotometry. 

W3 Cluster The photometry is not accurate enough to seardi for excesses. The E-band luminosity frmction is fit by a power law with a = 0.23 consistent with a 0.5 Myr duster with a Miller-Scalo IMF. 

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