Summary
What is Physics?
a. Science And Scientific Method
Science is exploring, experimenting, and predicting from what we see around us. ie. It is basically a systematic attempt to understand natural phenomena.
b. Physics
Two approaches are used in Physics: unification and reduction. In unification, diverse physical phenomena are explained in terms of a few concepts or laws. For example, all-electric and magnetic phenomena can be explained by laws of electromagnetism (Maxwell’s equations).
In reduction, we derive properties of complex (bigger) system from properties and interactions of constituent parts. For example, the temperature of system is related to average kinetic energy of molecule of system.
Scope And Excitement Of Physics
The different subdisciplines of physics belongs to two domains: the microscope domain and the macroscopic domain. The macroscopic domain includes phenomena at laboratory, terrestrial and astronomic scales.
The microscopic domain of physics deals with the constitution and structure of matter and their interaction with elementary particles like electron, proton, photon etc.
Physics covers a wide range of magnitude of physical quantities like length, time, mass, energy, etc. Physics includes phenomena involving elementary particles like electron, proton etc. whose range is 10-14m.
It also deals with astronomical phenomena at the scale of even the entire universe (10+26m). The range of time extends from 10-22 s to 1018s. The range of mass goes from 10-30 kg (mass of electron) to 1055kg (mass of entire universe).
Physics, Technology And Society
The relation between Physics, technology and society can be seen in many examples. The steam engine has an important role in the Industrial Revolution in England in eighteenth century. The discovery of basic laws of electricity and magnetism contributed wireless communication technology.
Fundamental Forces Of Nature
There occur four fundamental forces in nature. They are gravitational force, electromagnetic force, strong nuclear force and weak nuclear force.
1. Gravitational Force:
It is a universal force. Gravitational force is the attractive force existing between any two bodies by virtue of its mass.
2. Electromagnetic Force:
The electromagnetic force exist between charged bodies. The electrostatic force of attraction or repulsion exist between charges at rest. A moving charge has magnetic effect in addition to electric effect. The electric and magnetic effects are inseparable and hence force experienced by charge is called electromagnetic force.
3. Strong Nuclear Force:
The strong nuclear force binds the nucleons (protons and neutrons) inside the nucleus. It is the strongest of all fundamental forces. The range of nuclear force is 1o-15m (fermi) and it is charge independent.
4. Weak Nuclear Force:
The range of weak nuclear force is 10-16m. This force exists only in few nuclear, reactions like b-decay.
5. Towards Unification of Forces:
Isac Newton unified terrestrial and celestial domain by applying law of gravitation in two domains. Oersted and Faraday showed that electric and magnetic phenomena are inseparable. Maxwell unified electromagnetism and optics by showing light is an electromagnetic wave.
1.5 Nature Of Physical Laws
The physical quantity that remains unchanged in the process is called conserved quantity. Some of the conservation laws in nature are laws of conservation of mass, energy, linear momentum, angular momentum, charge, etc.
Conservation laws have a deep connection with the symmetries of nature. The symmetry of nature w.r.t. translation in time is equivalent to conservation of energy. Similarly, the symmetry of nature w.r.t. translation in space is equivalent to conservation of linear momentum.
Symmetries of space and time and other types of symmetry play an important role n modern theories of fundamental forces in nature
