Simulation of a variable-wavelength uv-visible spectrophotometer
with a 200 - 700 nm wavelength range, switchable tungsten and
deuterium light sources, four interchangable quartz cuvettes,
percent transmission and absorbance readout, auto-zero button, and
realistic sources of error and non-linearity. Students specify
sample characteristics, select wavelength, cell path length,
select deuterium or tungsten lamp, and perform measurements.
Realistic modeling of lamp spectral characteristics, cell
transmission variations, photon and detector noise, unabsorbed
stray light, and instrument non-linearity caused by finite
Version 1.2 (June, 2000) has a fixed 5 nm spectral bandpass and
models a single absorber in solution. Allows the student to
specify the solute weight, solution volume, and the absorptivity,
peak wavelength, and peak width of the absorber in each of the
four cells. Useful for reinforcing the Beer-Lambert Law and its
limits and for introducing the effects of noise and non-linearity
due to optical deviations from the Beer-Lambert Law.
Version 1.3 is similar to version 1.2, with the addition of a
"Statistics" button that takes 30 absorbance readings
automatically (without removing and replacing the cell) and
calculates the mean (average), standard deviation, and percent
relative standard deviation of the absorbance.
Specify the spectral characteristics and concentrations of the
absorbers in the four cell by typing values into the table (cells
C9 .. F13). Use the slider above to change the wavelength of the
instrument. Click on the buttons on the left to change the cell
path length and lamp type. Click on one of the four cell buttons
(#1 ... #4) to change the cell contents; this simulates removing
the cell, replacing its contents, and replacing it in the light
beam. Click the Auto-zero button to zero the instrument on the
current cell contents. Click the Read button to take another
reading of absorbance without disturbing the cells.