1. Classical Physics: This deals with the fundamental principles and laws of physics that were developed before the 20th century. It includes:

* Mechanics: The study of motion and its causes (Newtonian mechanics, kinematics, dynamics, etc.)

* Thermodynamics: The study of heat and its relation to other forms of energy.

* Electromagnetism: The study of electric and magnetic fields and their interaction.

* Optics: The study of light and its properties.

* Acoustics: The study of sound and its properties.

* Fluid Mechanics: The study of the behavior of fluids (liquids and gases).

2. Modern Physics: This deals with the physics developed in the 20th century and beyond, which involves quantum mechanics, relativity, and other more recent advancements. It includes:

* Quantum Mechanics: The study of the behavior of matter and energy at the atomic and subatomic levels.

* Relativity: The study of the relationship between space, time, gravity, and motion, particularly at very high speeds or in strong gravitational fields (Special Relativity and General Relativity).

* Nuclear Physics: The study of the structure, properties, and interactions of atomic nuclei.

* Particle Physics: The study of the fundamental particles that make up matter and the forces that govern their interactions.

* Astrophysics: The study of the physical properties and evolution of celestial objects and phenomena.

* Cosmology: The study of the origin, evolution, and large-scale structure of the universe.

It's important to note that these two divisions are not strictly separate. There are many overlaps and connections between classical and modern physics. For example, classical mechanics provides the foundation for many concepts in quantum mechanics.