The scope of physics is wide, covering a tremendous range of magnitude of physical quantities. Basically, There are two domains of interest: macroscopic and microscopic.
- The macroscopic domain includes phenomena at the laboratory, terrestrial and astronomical scales.
- The microscopic domain includes atomic, molecular and nuclear phenomena.
Classical Physics deals mainly with macroscopic phenomena and includes subjects like Mechanics, Electrodynamics, Optics and Thermodynamics.
Mechanics founded on Newton’s laws of motion and the law of gravitation is concerned with the motion (or equilibrium) of particles, rigid and deformable bodies, and general systems of particles.
Problems of Mechanics:-
- The propulsion of a rocket by a jet of ejecting gases,
- Propagation of water waves
- Sound waves in air
- The equilibrium of a bent rod under a load, etc.
Electrodynamics deals with electric and magnetic phenomena associated with charged and magnetic bodies. Its basic laws were given by Coulomb, Oersted, Ampere and Faraday, and encapsulated by Maxwell in his famous set of equations.
Problems of Electrodynamics:-
- The motion of a current-carrying conductor in a magnetic field
- The response of a circuit to an ac voltage (signal)
- The working of an antenna
- The propagation of radio waves in the ionosphere, etc.
Thermodynamics, in contrast to mechanics, does not deal with the motion of bodies as a whole.
Rather, it deals with systems in macroscopic equilibrium and is concerned with changes in internal energy, temperature, entropy, etc., of the system through external work and transfer of heat.
Problems of Thermodynamics:-
- The efficiency of heat engines and refrigerators
- The direction of a physical
- The chemical process, etc.
The microscopic domain of physics deals with the constitution and structure of matter at the minute scales of atoms and nuclei (and even lower scales of length) and their interaction with different probes such as electrons, protons and other elementary particles.
Classical physics is inadequate to handle this domain and Quantum Theory is currently accepted as the proper framework for explaining microscopic phenomena.
Recently, the domain intermediate between the macroscopic and the microscopic (the so-called mesoscopic physics), dealing with a few tens or hundreds of atoms, has emerged as an exciting field of research.