(A Processing program for visualising refection)

Charlotte Bond


This applet illustrates the change in amplitude, wavelength and phase of electromagnetic waves as they cross a boundary between two different optical media. The modelled wave interacts with the boundary at normal incidence. This applet allows you to vary the optical parameters of the wave, specifically the amplitude, wavelength and speed of the wave, and also allows you to alter the refractive index of the two materials. There are also options to change the type of wave, from a simple Gaussian ‘bump’, to a sinusoidal wave, to a ‘photon-like’ representation, a combination of a Gaussian bump and sinusoidal wave. The applet also allows you to view either all parts of the wave or simply the continuous components, as well as allowing the user to look at either the electric or magnetic field

This applet has been built with Processing and makes use of the G4P (GUI for Processing) library.

The sliders can be used to change several parameters of the interferometer:
  • Length of second arm – This controls the position of the second mirror
  • Reflectivity: beam-splitter – This controls the power reflectivity of the beam-splitter
  • Reflectivity: first mirror – This controls the power reflectivity of the first mirror
  • Reflectivity: second mirror – This controls thepower reflectivity of the second

When the electromagnetic wave hits the boundary at normal incidence, part of the wave is reflected backwards, in the opposite direction to the incoming wave. The reflected and incoming waves interfere with each other, adding together to give a resultant wave on one side of the boundary, in the first material. When the wave hits the boundary part of the wave is transmitted through the second material. The transmitted wave and the wave resulting from the interference of the reflected and incoming waves must have the same value at the boundary, due to boundary conditions derived from Maxwell’s equations. These boundary conditions state that, for materials with no free current or charge density, the components of the D- and B-fields normal to the boundary must be continuous and the components of the E- and H-fields parallel to the boundary must be continuous.