The point of Physics Electives are to prepare you for potential jobs and/or for grad school. Electives for your degree should be chosen based on if you are interested in doing it for a job or to help out a minor. Most universities require you to take two 4xxx elective courses for your degree.
Most Physics Electives are 3xxx or 4xxx level courses and have the prerequisite of Physics II but depending on the course it would be in your interest to have taken some other courses first. For example Intro to Quantum Computing typically benefits from having taken Quantum Mechanics I and Biophysics benefits from having taken Thermal Physics. Asking other students that have taken the course to see what they wish they had taken or what they benefited from knowing is in you best interest.
Physics Electives vary between Universities. Not every school offers every course. Some are even known for the ones they do offer. These courses are very important as they are some of the few courses you actually get to choose for yourself that are within your major. So, take time in considering which ones to take. It is also worth asking your advisors if you are able to select electives from other majors. This is an especially important option if you intend to go to graduate school in a different major, if you know what job you want to to get and it could help, or if you want to broaden your horizons and see what other fields are like. Some common Physics Electives are:
If you are interested in Astrophysics look for these course.
Observational Astrophysics: is a hands on lab course which involves using telescopic observations of celestial objects including the moon, planets, stars, interstellar medium, and galaxies.
INTRO ASTROPHYSICS: Extends basic Newtonian mechanics to determine dimensions, masses, luminosities, structures, and evolution of astronomical objects and the universe as a whole. This is a lecture based course that is not typically very hard but is incredibly interesting.
INTRO TO GENERAL RELATIVITY: Introduction to methods and applications of Einstein’s general theory of relativity. Some topics include space and time and gravity in Newtonian physics; special theory of relativity, gravity as geometry of curved space-time.
If you are interested in Nuclear Engineering or Particle Physics
FOUNDATIONS OF NUCLEAR AND PARTICLE PHYSICS: Introductory nuclear and particle physics, presenting experimental basis, applications, and future directions. This includes special relativity, statistical physics, nuclear structure, radioactivity, reactions and nuclear applications, and elementary particle physics.
INTRODUCTION TO NUCLEAR AND PARTICLE PHYSICS: Structure and properties of atomic nuclei and elementary particles, theoretical interpretations based on elementary quantum mechanics.
If you are interested in applications of Quantum Mechanics and semiconductor technology
FOUNDATIONS OF QUANTUM AND SOLID STATE PHYSICS: Covers quantum and solid state physics with applications to engineering materials and devices. Wave-particle duality, Schrodinger wave equation, atoms and molecules, crystal structures, x-ray and neutron diffraction; energy band theory, electrical and thermal transport properties of metals, insulators, and semiconductors.
INTRODUCTION TO SOLID STATE PHYSICS: Basic concepts of solid state physics including crystal structure, lattice vibrations, electron states, energy bands, semiconductors, metals.
NANOTECHNOLOGY: Introduction to methods of controlling matter on the nanometer length scale and the applications. Self-assembly, and scanned probe microscopy, carbon nanotubes, and quantum dots
If you are interested in applications of Electricity and Magnetism or applications of Thermal Physics
OPTICS: Fundamentals of the ray, wave and quantum models of light, and topics in modern optics with contemporary applications.
INTRODUCTION TO BIOPHYSICS: Includes the general area of biomechanics, bioelectricity, radiation biophysics, molecular biophysics, and thermodynamics and transport in biological systems. Emphasizes physical aspects of biological phenomena and biophysical measurement techniques.