Making a web app is a mistake 9 times out of 10, particularly when dealing with larger datasets. Because you're in physics, you probably want to skills you're learning to be transferable into physics and data science in general.

I recommend starting with python (if you know it already, awesome), then checking out pyqtgraph -- there's a bunch of demo apps that come with the package and you can use those as launch points. This will be your gateway into pyqt/pyside and legit desktop application development. Later, if you learn C++, you can transition into Qt (and still use all the power of the toolkit and the skills are transferable), or into raw C++ which is amazing for numerical computing.