50. Projected Mercury and Continuous Spectra

light spectrum

The arrangement below will project the lines of mercury just above their positions in a continuous spectrum of a tungsten filament. By adjusting the height of the 45° mirror you can have the entire length of the mercury lines, mercury lines above continuous spectrum, or just the continuous spectrum. Note that the spectrum of the tungsten filament is deficient in blue as befits a 3000° black body which peaks in the infrared.

Reference instructions for assistant:

  1. Focus Hg lamp on slit.
  2. Focus projection lens on screen
  3. Align mirror and W. lamp. (The W lamp has a single vertical filament so no slit or lens is necessary.)
  4. Focus W lamp for continuous spectrum.
  5. Align the two spectra by aligning mirror.
  6. Block any stray light with cardboard.