Midterm Flashcards
What is Beers Law? What can we determine from it?
Beer’s Law states that the concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light. We can determine the concentration from the absorbance or transmittance values.
Light Source of Spectrophotometer
Provides radiant energy at a consistent intensity
Tungsten lamps are used for visible light
UV light: deuterium
Visible and UV: mercury
Monochromator
Allows for isolation of radiant energy of a specific wavelength using filters, prisons, diffraction grating etc.
Prism
Prism or grating splits radiant energy into continuous spectrum of various wavelengths
Collimator
Collects as much light as possible on the entrance slit
Sample Holder
For placement of solution within cuvette
o Cuvette that holds sample solution to be measured.
o Generally made of plastic with a light path of 1cm in length.
o Avoid using scratched cuvettes and wipe away oil, fingerprints, dust, and other debris with a Kim
Wipe prior to inserting into sample holder.
o Usually has an orientation (designated by an arrow, triangle, or a clear versus opaque side) so the user aligns the cuvette correctly in the light path
Photodetector
Converts the transmitted light from the sample into an electrical signal
o Different spectrophotometers use different photodetectors: photocell, phototube, photomultiplier tube, photodiode array, etc.
Parts of a spectrophotometer
Light source, monochromator, sample holder & photo detectors
What is a spectrophotometer?
an instrument that can measure the amount of monochromatic light (radiant energy of one wavelength) that can be absorbed or transmitted through a solution
Diffraction Graftings
Spectrum resulting from light striking a surface engraved with many parallel lines
