We must know these numbers to specify the filters we need to generate fluorescence. When we have this information then we can get the correct exciter, dichroic and barrier filter. Most manufacturers put all these filters together in a unit, called a cube, that fits into the universal illuminator. There will also be cubes for bright field and dark field. Changing cubes is a simple as moving a lever.
Manufacturers make cubes for all the most popular materials techniques such as photo resist.
There are very good third party filter makers that can produce filters and dichroics in just about any wavelength and install them in a cube for your microscope. What this means to you Fluorescence is a valuable technique in materials science. You need to know the excitation and emission of the fluorochrome you are looking for. Lots of light is a must. Manufacturers have the tools ready for this technique.