My questions are 1) The incident power of the beam of light is reduced by 50% an

Question

My questions are

1) The incident power of the beam of light is reduced by 50% and passing through 1 cm of an analyte solution. What will be the reduction after going through 1.5 cm of the same solution ?

2) what is the theoretical signal to noise ratio improvement for a CCD with 1024 channels compared to a scanning monochromator with a PMT, assuming equal noise in both detectors?

3) estimate the fraction of light that is lost by Fresnal reflection through a double pane plate glass window and explain how you arrived at your answer

Explanation / Answer

1)

The Beer-Lambert Law. In absorption spectroscopy, the intensity I of light passing through an absorbing sample is given by the Beer-Lambert Law:

I = Io*10-(alpha*L*c)

where “Io” is the intensity of the light incident on the sample, “alpha” is the absorption coefficient or the absorptivity of the absorber, “L” is the distance that the light travels through the material (the path length), and “c” is the concentration of absorber in the sample. The variables I, Io, and alpha are all functions of wavelength; L and c are scalar

So, 0.5 = 10-alpha*L*c => log(Io/I) = alpha*L*c   

So, L is proportional to log(Io/I)

[log(Io/I)]2 = [log(Io/I)]1 (L2/L1) = 0.301*1.5 = 0.4515 => Io/I = 2.828 => I = 0.3535 Io

  Reduced to 35.35 % of Io

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