Tutorial details

The tutorial begins with some of the same questions as on the pretest. Students are given the diagrammatic and algebraic representations and asked to determine the direction of propagation of the wave and rank four points according to (1) the magnitude of the electric field and (2) the magnitude of the magnetic field. Few students spontaneously recognize that the algebraic representation can be used to determine that the electric field is the same at points that have the same x coordinate but different z coordinates. Students are led to recognize that for a plane electromagnetic wave, the electric (and magnetic) field is the same at all points in a plane perpendicular to the direction of propagation. Students then interpret diagrammatic representations of EM waves that have different amplitudes and wavelengths.

In the next part of the tutorial, students are guided to understand how a wire can be used to detect an electromagnetic wave. In the final part of the tutorial, students are led to relate Faraday’s law to an EM wave. They use Faraday’s law to argue that it is not possible to have the same electric field as discussed above with a magnetic field that is zero for all x and t.

For instruction tips, login or register as a verified educator to see the Instructor Guide.

It is expected that students have studied some electricity and magnetism. In particular, they must be familiar with the Lorentz force equation and Faraday’s law. The last page of the tutorial may be difficult for students with weak backgrounds in mathematics.

Equipment

List

• handouts
• white board or large sheet of paper with markers

Discussion