Radiation protection - how to ensure that users of radiation do not get excessive exposure.
Spectroscopy - The science of telling what sort a chemical something is by looking at its quantised spectra.
Burglar alarms - how they are basic thermal imaging cameras.
I have to do a talk on an application of the EM spectrum for my course, I know everything there is to know already but don't want to be boring or too technical for the rest of the group.
I will not bump this thread, if it dies; it dies.