Branches of Physics

Physics is basically divided as physicists went on exploring nature at deeper levels,  into the following different branches. However it must be kept in mind that these divisions are done to facilitate our own understanding, the Nature has not compartmentalized itself.

Mechanics  deals with the behavior of objects and systems in response to various forces.

(Classical Mechanics describes motion of objects on large scale (macroscopic level) while Quantum Mechanics deals with phenomena on sub-atomic (microscopic) level.
 
Thermodynamics is the study of heat and other forms of energy, and of the conversion of energy from one form to another. 

Optics is the study of the nature and behavior of light. 

Electromagnetism analyses the relationship between electrical and magnetic forces. 

Geophysics is the study of earth and its atmosphere and waters by means of the principles of physics. 

Nuclear physics is concerned with the structure and properties of the atomic nucleus, and with nuclear reactions and their applications. 

Solid-state physics examines the physical properties of solid materials. 

Acoustics studies the production and properties of sound. 

Molecular physics examines the structure, properties, and behavior of molecules. 

Particle physics also called high energy physics, analyses the behavior and properties of elementary particles.  

and then there are many others, including the inter disciplinary ones, such as Astrophysics, Bio Physics,  etc.