3) Scientists measure the amount of light passing through a sample in terms of p

Question

3) Scientists measure the amount of light passing through a sample in terms of percent transmittance (%T). Percent transmittance is the fraction of original light that passes through a sample. Recall that P0 is the amount of light entering the sample and P is the amount of light reaching the detector. Using a spectrometer, a sample was analyzed to have a percent transmittance of 85%. What percentage of light was actually absorbed by the sample? (1 points)

%T= P/P0 * 100

4) The equation below shows how percent transmittance (%T) can easily be converted into a quantity known as absorbance (A). Though most spectrometers give readings in terms of both %T and A, measurements should be made in %T and mathematically converted to A because %T can be determined more accurately. Calculate the absorbance of a sample that has a percent transmittance of 75%. (1 points)

A=-log(%T/100)

Explanation / Answer

3) % of absorbance = 100 - % transimittance

                                = 100 - 85

                                = 15%

4)    A = - log (%T/100)

Absorbance (A) = - log (75/100)

                          = - log (0.75)

                         = 0.1249

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