My research has spanned the electromagnetic spectrum from quasi-statics at 1KHz to optics in the visible spectrum, passing through microwaves and infrared along the way. I have also worked in acoustics and ultrasonics both in water and air. From a theorist's perspective, a wave is a wave, but from the experimentallist's perspective, these different physics and frequency regimes require different skill sets.
Different scientists are motivated by different things. Personally, I take great satisfaction in the moment when theory and experiment align in something counterintuitive. Much of my work is reaching toward that moment. This is done by refining my analysis to include the complications of experiment and striving to simplify the experiment to the point where it can actually be analyzed.
However, my own gratification is not the purpose of my work and the world has too many problems for "Art for the Sake of Art." Science and Engineering have the ability to change the world in ways we can't even imagine, both for good and evil. I strive to have what comes off my desk change the world for the better.