Question
Spectroscopy is an important tool to measure light wavelengths pertaining to a variety of chemistry, physics, biochemistry, material and chemical engineering, and clinical applications. Beer-
Spectroscopy is an important tool to measure light wavelengths pertaining to a variety of chemistry, physics, biochemistry, material and chemical engineering, and clinical applications. Beer- Lamberts law relates the transmitted light intensity, I, to the incident light intensity, I0, according to the following relationship:
= # 10()*+
where a is a wavelength-dependent constant called the extinction coefficient of the sample, b is the light path length (i.e., path distance) through the sample, and c is the sample concentration. Experimental measurements of the path distance at 0.1-cm intervals are given in the following
table. The extinction coefficient is ,### - and the concentration is 18 mM. Note that path length
(b) is the variable in this question.
.01
Distance (cm) | Intensity (arbitrary units) |
0.0 | 1000.0 |
0.1 | 990.8 |
0.2 | 981.7 |
0.3 | 972.7 |
0.4 | 963.8 |
0.5 | 954.9 |
0.6 | 946.2 |
0.7 | 937.5 |
0.8 | 928.9 |
0.9 | 920.4 |
1.0 | 912.0 |
This above equation can be rewritten as follows:
log5#() = log5#(#) which could result in a straight line with slope and intercept log5#(#).
-
(a) Plot the measured data (as shown in table) as red circles.
-
(b) Carry out a first-order polynomial fit to model the measured data. Find the slope and intercept
of the straight line.
-
(c) Calculate the slope based on your curve fitting results. Compare your results to (given above).
-
(d) Calculate the value of I0 based on your curve fitting results.
-
(e) Calculate new values of based on your polynomial fit, over a range 0.0 1.0.
-
(f) In a new plot, plot the logarithm (base 10) of on the y-axis and b on the x-axis using (i) measured data as red circles, and
(ii) linear polynomial fit as a blue solid line.
Label the axes and give an appropriate title to the plot. Include appropriate legend showing measured data and linear fit.
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