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
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.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.