Ge 214, Spectroscopy of Minerals

Class Notes for Students

General Information

Wavelength & Color  Units & Terms  References
 

1) Wavelength and Color


The entire spectrum
  Wavelength (nm) Color 
~730 onset of human vision
  700 deep red
  660 red
  610 orange-red
  600 orange
  590 yellow-orange
  580 orangish-yellow
  570 yellow
  565 yellow-green
  550 green
  530 pure green
  500 bluish green
  498 blue-green
  490 greenish-blue
  480 blue
  470 indigo
  460 blue-violet
  440 violet
~360 cutoff of human vision

 These colors are necessarilly approximate and depend on the settings of your monitor and the phosphors in the screen.
 

2) Units and Terms:


  Wavelength   (l)

 1 nm 10-9  m
 1 mm 10-6  m
 1 Å 10-10 m

  Frequency       n  = c/l  Hz
                  _
  Energy      n = 1/l      cm-1 (wavenumbers)  [occasionally presented in mm-1]
                                   1 mm-1  = 10-4 cm = 104 cm-1 = 10,000 cm-1
                                   1 ev      =  8068 cm-1
                                   1 cm-1  =  2.859 calorie per mole of photons

  Absorbance =   e * path (cm) * concentration (moles per liter) = -log10(I/I0)

  Internal Transmittance = T = I/I0        (ignores reflections, etc. at the boundary)

  0.6 T = 60% T                                  (instruments sometime read %T)

  e  =  molar absorption coefficient        (formerly called extinction coefficient)

  c = 299,792,458 km sec-1