Multimedia in Physics Education

A Video for Teaching on „Birefringence and Polarization in Calcite“

Stefan Altherr, Andreas Wagner, Bodo Eckert, Hans Jörg Jodl

University of Kaiserslautern, Department of Physics
Erwin-Schrödinger-Straße, 67663 Kaiserslautern, Germany

Starting from a phenomenological observation we systematically examine and ana-lyze the double diffraction in the video on “Birefringence and Polarization in Calcite”. The movie conceived for teaching presents a vivid linkage of real experiment and theoretical knowledge from the textbooks.

Presently, Birefringence is not a standard ex-periment in lectures at university. Thus, the presentation is limited to textbooks. Currently, only two videos on the topic can be found. Both only show the phenomenon of double diffraction and surrender further analysis [1].
The experiment “Birefringence and Polarization in Calcite” examines the direction dependency of the velocity of propagation of light in non-isotropic crystals. Basic concepts are intro-duced and polarization of light-bundles is in-vestigated.

The intention of the movie, produced at the University of Kaiserslautern is to study the birefringence in calcite systematically. Fur-thermore it explains the results theoretically, starting from an introduction that corresponds with the figures in textbooks [2].

Fig. 1: Phenomenological introduction

In the beginning, the video establishes the phenomenological view of the double diffrac-tion (Fig. 1).
Thus it ties in with the textbooks and offers descriptive and motivating access. The experimental setup is revealed with stop-motion technique (Fig. 2).
So, all components are presented step by step and explained in their functionality. In doing so, the viewer can access the experiment easily. Each component of the setup is shown enlarged and thereby easy to identify.

Fig. 2: Setup (f.l.t.r.: Hg-spectral-lamp, aperture plate, calcite-crystal, analyser)

Starting with a side view of the setup (see Fig. 2), a camera pan, which reveals a view through the analyzer, follows, showing the correlation between setup and result.
One recognizes, that only one light-bundle is entering the calcite, but two are leaving.
The first noted result is the splitting of the light inside the crystal.
Next, the polarization of the leaving beams is analyzed. Therefore, the analyzer is rotated until one, then the other light-point disappears. The according angles are noted graphically. (Fig. 3)
The light intensity changes depending on the angle of the analyzer.

Fig. 3: Polarisation of the light beams in correlation

At the end of the analysis, performed in the video, the right-angled polarization of the light beams with respect to each other is displayed (Fig. 3).
To help the viewer to understand this result, the important terms principal axis, ordinary and extraordinary ray are illustrated by laying transparent, three-dimensional drawings over the calcite-crystal used in the experiment (Fig. 4).

Fig. 4: Explanation of principal terms

These abstract definitions are then transferred back to the experimental setup, helping thereby the viewer in understanding and fur-ther interpreting the findings (Fig. 5).
Finally the observations are summarized and the final statement established:

  1. Splitting of the light in two beams
  2. Ordinary and extraordinary ray are diffracted differently
  3. Right-angled polarisation of the light beams with respect to each other
The video experiment provides the complete procedure from observation of birefringence, the presentation of the experimental setup to the analysis of the phenomenon and systematic investigation.

Fig. 5: Principal terms of the experiment with inserted calcite (see Fig. 4)

Thereby, the video is more demonstrative then static pictures in textbooks and furthermore it is able to point out terms and correlations theo-retically and practically. With this video the dependence of light propagation and polariza-tion is examined.
The video can be used in lectures and also in self-studies. Depending on its embedding in a teaching environment, it can be used at school and also in beginners´ courses at university.

The video “Birefringence and Polarization in Calcite” is available form the authors on CD-Rom for a protective charge of 5 €.


[1] e.g.:
a) Nave, C.R.: Hyperphysics, Department of Physics and Astronomy, Georgia State University,
b) Higatsberger M.J.: Physik in 700 Experimenten, Experiment 675, Institut für Experimentalphysik, Universität Wien,
[2] See for example:
a) D. Halliday, R. Resnick: Physics, 4th extended Edition, New York: John Wiley & Sons, Inc., 1992
b) Gobrecht, H. (Hrsg.): Bergmann – Schäfer – Lehrbuch der Experimentalphysik, Band III: Optik, 8. Auflage, Berlin: Walter de Gruyter , 1987.
c) Meschede, D.: Gerthsen Physik, 21., völlig neubearbeitete Auflage, Berlin: Springer, 2002.