MODERN PHYSICS LAB

Absorption and Line Spectra

OBJECT:

        To produce both line and absorption spectra using a variety of sources

EXPERIMENT 1:

  1. Place a pinhole in front of a white light source and focus the pinhole's image on the entrance slit.  Perform a  scan to display the continuous spectrum of the white light source utilizing the Science Workshop interface, i.e.  scan from 4000 to 7000 at 500 /min while recording the intensity data on the computer.  You will have to convert the time axis on the graph to wavelength.       

  2. Replace the white light source with a high intensity mercury lamp.  Turn the mercury lamp on and allow it to "warm up" for several minutes while you prepare for the measurements of this part. Mercury has a characteristic spectrum which has several strong lines with visible wavelengths.  Again, scan from 4000 to 7000 at 500 /min while recording the intensity data on the computer.  

  3. By selecting a much narrower scan region and scanning at a much slower speed, one can investigate individual spectral lines and the effects of changing slit widths for this spectrometer.   Single line profiles can be studied using the Green line of mercury at 5461 .  The resolution of multiple lines can be studied using the Yellow doublet at 5790 and 5791 .

EXPERIMENT 2:

Absorption Spectra will be investigated in this experiment.  The white light source will be used as the initial source, and various absorbing media will be inserted into the beam.  Scans of the white light spectrum before and after absorber insertion will be compared.   Absorption can be observed using:

Scale the white light spectrum from Experiment 1 and use it tto obtain normalized absorption spectra for the crystals and the glass.  Zoom in on regions of interest.