# Unclear units for Electromagnetic Field Simulation

I am working with a simulation of electromagnetic fields. After reading the modulus user guide, I have some doubts about the units used in the modulus samples, especially the wavenumber (frequency divided by the speed of light). When we usually simulate the electromagnetic field in Matlab, the unit of length, width and height of the electrolyte space is nm or micrometer, and the unit of transmitted wavelength is also nm.
In my simulation, the space unit is microns, and the wavelength of electromagnetic waves is 500 nm. The results simulated by modulus are different from those of matlab. I am sure that other settings are no problem, mainly the problem of units.
In Chapter 10 of the User Guide, all the examples are unitless, with wave numbers of 16 or 32, as shown in the figure below.

I want to know what are the spatial units used in the modulus and also what are the frequency units of the electromagnetic wave.

Thanks and regards,

Zhou

For all problems using Modulus we typically suggest users scale/nondimensionalize the problem to be centered around 0 and has a reasonable domain range. This practice is essential for successful deep learning of physical systems, akin to scaling training data. Thus in this example, think of the domain length of having a nondimensionalize unit (say m*) and the wave number also being applied in that nondimensionalize space (1/m*).

So for your particularly problem where the space unit is micron, you would want to scale/nondimensionalize the system to get the best results from physics-informed deep learning.

We have some information/resources on this process in the docs here:
https://docs.nvidia.com/deeplearning/modulus/user_guide/theory/recommended_practices.html#scaling-the-problem