Polarized Light

Springer, Ellen                        Nazareth Academy
                                       1-708-354-0061
                           
Objectives

1) To expose students to the basic behavior of polarized light. 
2) To help students discover that light can be polarized by reflection from a non-
   metallic surface as well as by passing through certain crystalline materials. 
3) To develop a model which can account for differences in light behavior using a 
   second set of polaroid filters. 

Equipment and Materials

2 polarizing filters with axes parallel to the edge. 2 polarizing filters with axes 
45o to the edge. Distinguish from the above filters by placing them in colored 
holders. microscope slide, cheap scotch tape (Le Pages or Tuck are good.) plastic 
champagne glass, shiny metallic surface (aluminum foil), shiny non-metallic dark 
surface (student folder may be useful here.) 

Recommended Strategy

1. Place one polaroid filter between eye and a light source (window is good); slowly 
rotate the filter.  Note any changes in light intensity. 

2. Place a polaroid filter in front of a light source.  Slowly rotate a second 
polaroid filter between your eye and the other filter.  Note any change in light 
intensity. 

3. Put a single strip of scotch tape on one end of the microscope slide, and  several 
pieces crossed on top of one another on the other end.  Place the slide between the 
filters and slowly rotate one of the filters.  Slowly rotate the slide.  Note any 
change in light intensity or other phenomenon. 

4. If available, show the segment on polarized light from Newton's Apple. 

5. View light reflected from both a shiny metallic surface and from a non-metallic 
surface using one filter and rotating it slowly.  Note any change in light intensity 
of the reflected light. 

6. View a plastic champagne glass placed between two polaroid filters.  Now place the 
glass on the glare area of a shiny non-metallic surface, and view it through one 
polaroid filter.  Ask students to explain the origin of the colors even though only 
one filter is used. 

7. Obtain a second set of polaroid filters (in colored holders).  Compare the 
behavior of light through both sets of filters when one filter is: a) rotated, b) 
placed in front or behind the other, c) flipped over. 

8. Challenge students to develop a model which will explain the difference in the 
behavior of light in 7 c above. 

9. View a liquid crystal display through one polaroid filter rotating the filter 
slowly.  Note any change in light intensity.  A good explanation of the way that a 
liquid crystal display operates and other information about polarized light can be 
found in the student publication, Chem Matters, April 1984, pp. 8-13.