7B11.80 - Spectral Lines/Spectroscopy - Food Coloring

Code Number:
7B11.80
Demo Title:
Spectral Lines/Spectroscopy - Food Coloring
Condition:
Excellent
Principle:
Spectra of Various Gases, Spectral Lines of Elements
Area of Study:
Optics, Astronomy

Disclaimer

Equipment:
Holographic grating, Overhead slit mask, White Light Projector, Glass Cell, Food Coloring, Stirring Rods, Large Beakers (2000 ml).
Procedure:

See also 7B11.80 in Modern Physics.

A band absorption may be produced by putting a water cell into the light path of the overhead projector or white light projector.  A couple of drops of food coloring stirred into the cell will produce broad band absorption.  Dr. Neff likes to do this in reverse!!  He likes to start with food colored water and show the band.  He then dilutes the colored water to make the band disappear.

References:
  • "Figuring Physics", TPT, Vol. 43, # 2, Feb. 2005, p. 117.
  • Kenneth Brecher,  "Do Atoms Really 'Emit' Absorption Lines?",  TPT, Vol. 29, # 7, p. 454, Oct 1991.
  • Don Hruby, "Doing Physics", TPT, Vol. 25, # 6, Sept. 1987, p. 402.
  • O-285:  "Holographic Grating-Antifreeze",  DICK and RAE Physics Demo Notebook.
  • O-740:  "Fabrics & Theatrical Filters",  DICK and RAE Physics Demo Notebook.
  • Ron Hipschman, "Color Removal", Exploratorium Cookbook III, pp. 174.1 - 174.3.
  • 2.5:  Charles Taylor,  The Art and Science of Lecture Demonstration, pp. 70-71.

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