Classical mechanics: Classical mechanics is the basis of physics, which studies the laws of motion of objects under the action of force, including Newton mechanics and Lagrange mechanics.
Electromagnetism: Electromagnetism studies the interaction between electric charge and electric field, including electrostatics, electrodynamics and electromagnetic waves.
Thermology: Thermology studies the laws of temperature, thermal energy and thermodynamics of objects, including thermodynamics and statistical physics.
Optics: Optics studies the propagation, diffraction and interference of light, including geometric optics and physical optics.
Atomic physics and quantum mechanics: Atomic physics and quantum mechanics study physical phenomena in microscopic fields, including atomic structure, basic principles of quantum mechanics and particle physics.
These levels are usually the main content of college physics courses, and also an important field of physics research.