Electromagnetic waves in matter

Equipment

• Virtual plane wave traveling through a dielectric block
• Amplitude/source, wavelength, frequency, and view sliders
• Model A/B buttons and Pause
• Readouts $v=c/\sqrt{\varepsilon_r}$ and $k=n\omega/c$

Procedure

1. Measure the wave speed in the medium

   In figure 1, read $v=c/\sqrt{\varepsilon_r}$ and compare with the displayed wavelength: in a dielectric with $\varepsilon_r>1$ the wave slows and λ shrinks by the same factor, while the source-set frequency f stays constant.

2. Observe dispersion and attenuation

   In figure 2, raise the material parameter: the wave carries a complex wave number $k=k'+i\kappa$ so the amplitude decays as $e^{-\kappa z}$ — read the attenuation on the readout and compare the amplitude slope as the parameter grows.

3. Compare vacuum and medium

   Toggle between model A and B (equivalent to vacuum/material regions): at the same frequency the in-medium wave has a shorter λ and its amplitude changes at the boundary — a consequence of the reflection coefficient $r=(\eta_2-\eta_1)/(\eta_2+\eta_1)$ with $\eta=\sqrt{\mu/\varepsilon}$.

Simulation

Experiment history

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