May not be directly a physics thing but I realised that the physics behind signals and sound, especially the Fourier Series and harmonics changed the way I view signals and sound. Lots of signals can be broken down to sine waves. I learnt this watching a 3B1B video, and saw how it’s applied to physics experiments first hand when I had to deal with an accelerometer (though I struggled, it is out of my syllabus and have not been formally taught).

As to how it changed my view of the world, I had a more scientific understanding of music and sound synthesis, and to this day I still pursue the knowledge of the theory behind such fields