Background to matrix optics
Optical matrix applied to the centered systems

Light is an electromagnetic vibratory phenomenon, obeying the laws of electromagnetism in materials, modeled by Maxwell's equations. Its propagation is characterized by its spatial period $$\lambda =c\text{/}\nu$$ , called wavelength, ν being the frequency of the vibration and c its celerity (speed of propagation) in the material through which it passes.

In order to make the solution given by Maxwell's equations independent of the materials in which light propagates, vacuum is taken as the reference medium. Thus, a wave of frequency ν is characterized by its wavelength λ ₀ ...