Kerala Plus One Physics Notes Chapter 1 Physical World
Science is a systematic attempt to understand natural phenomena in as much detail and depth as possible, and use the knowledge so gained to predict, modify and control phenomena. Science is exploring, experimenting and predicting from what
we see around us.
The scientific method involves several interconnected steps:
- Systematic observations
- Controlled experiments
- Qualitative and quantitative reasoning
- Mathematical modelling
- Prediction and verification or falsification of theories.
- Speculation and conjecture
The word Science originates from the Latin verb Scientia meaning to know’.
Physics is the study of nature and its laws. We expect that all the different events in nature takes place according to some basic laws. We try to understand these laws from observing the nature.
All the physical theory was supported by mathematical formulations, but also supported with experimental proof. That is the beauty of physics. Every single fact of physics has experimental proof.
The word Physics comes from a Greek word meaning “nature”.
Two principal types of approaches in Physics are:
This approach considers all of the world’s phenomena as a collection of universal laws in different domains and conditions. Example, law of gravitation applies both to a falling apple from a tree as well as motion of planets around the sun. Electromagnetism laws govern all electric and magnetic phenomena.
2. Reduction :
This approach is to derive properties of complex systems from the properties and interaction of its constituent parts. Example, temperature studied under thermodynamics is also related to average kinetic energy of molecules in a system (kinetic theory).
Scope and Excitement of Physics
Physics is broadly divided into two types based on its scope – Classical Physics and Modern Physics. Classical physics deal with the macroscopic phenomena while the modern physics deals with the microscopic phenomena.
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.
It is based on Newton’s laws on motion and the laws of gravitation.
It is concerned with motion/equilibrium of particles, rigid and deformable bodies and general system of particles. e.g. Propulsion of rocket by ejecting gases,
Water/Sound waves .. etc.
It deals with electric and magnetic phenomena associated with charged and magnetic bodies. e.g., motion of a current-carrying conductor in a magnetic field.
It deals with phenomena involving light. e.g. Reflection and refraction of light, Dispersion of light through a prism.
It deals with systems in macroscopic equilibrium and changes in internal energy, temperature, entropy etc. of systems under application of external force or heat. e.g., Efficiency of heat engines, Direction of physical and chemical process.
Microscopic Domain :
Microscopic domain includes phenomena at minuscule scales like atomic, molecular and nuclear. It also deals with interaction of probes like electrons, photons and other elementary particles. Quantum theory has been developed to handle these 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.
Factors responsible for progress of Physics
- Quantitative analysis along with qualitative analysis.
- Application of universal laws in different contexts.
- Approximation approach (complex phenomena broken down into collection of basic laws).
- Extracting and focusing on essential features of a phenomenon.
Physics, Technology and Society
Sometimes Physics generates new technology and other times technology gives rise to new Physics. Both have impact on 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 to wireless communication technology in nineteenth century.
Fundamental Forces in Nature
(പ്രക്യതിയിലെ അടിസ്ഥാന ബലങ്ങൾ)
Force for us is either a push or a pull, it can be due to muscle, magnet or machine. Of all the early scientists, Galileo was the first to understand the nature of force. Newton was the first to explain it in a set of laws. At present, we have understood that all the forces in nature are mostly similar and can be grouped into four fundamental types of forces.
It is the force of mutual attraction between two bodies due to their masses. Every body attracts every other body of the universe with this force. It has no range limits. It is the weakest force in nature. Still this is the force that keeps our solar system stable, even the whole universe. Weak Nuclear Forces It is the force that appears only between elementary particles involved in a nuclear process such as the B-decay of nucleus. In B-decay, the nucleus emits an electron and an uncharged particle called neutrino. The range is very small, about 10-16 m.
The force acting between two electric charges at rest is called electrostatic force. The coulomb’s law gives the value of this force. Like charges repel and unlike charges attract. An electric conductor has a magnetic field around it. A copper wire moving in a magnetic field produces electric current. So we see that electricity and magnetism are closely related. So, the term electromagnetism. This force also has no range limits. This is stronger than the weak force by a factor of 10-16
Force The strong attractive force which binds together the proton and neutrons in a nucleus is called strong nulcear force. It is of a very short range 10-15 ……………metre. Electrons are not included in this range.
FG :Fw :FE :FS 1:1025: 1036: 1036
Gravitational force is the weakest fundamental force. Then how can it reach to cosmological distances?
The strength of gravitational force is proportional to the mass. Hence as the mass increases, the force strength increases and for planets and stars the gravitational force reaches to cosmological distances.
|Towards Unification of Forces|
|Physicist (s)||Achievement in unification|
|Issac Newton||Unified celestial and terrestrialdomains by explaining both types of phenomenaby applying the same laws of motion and law of gravitation|
|Hans Cristian Oersted Michael Farady||Showed experimentally that electric and magnetic phenomena are inseparable aspects of a unified domain called electromagnetism|
|James Clerk Maxwell||Unified electromagnetism and optics by discovering that light is an electromagnetic wave|
|Albert Einstein||Asserted the equivalence of mass and energy and unified the motion of space,time and gravitation in his theories of relativity|
Discuss grand unified theory (GUT)
According to Abdus Salam, Glashow and Steven, electro-weak force is a single force resulting from the unification of electromagnetism and weak and Sheldon Glashow proposed a theory known as grand unified theory (GUT)
- Physical quantities that remain constant with time are called conserved quantities.
- Conserved quantities can be scalar (Energy) or vector (Total linear momentum
and total angular momentum)
- Laws of conservation of mass
- Laws of conservation of energy
- Laws of conservation of linear momentum
- Laws of conservation of angular momentum
- Laws of conservation of charge
- Laws of conservation of parity, etc.
- Some conservation laws are true for one fundamental force but not for the other
- Conservation laws have a deep connection with symmetries of nature.
- The symmetry of nature w.r.t translation in time is equivalent to conservation of energy. Similarly the symmetry of nature writ translation in space is equivalent to conservation of linear momentum.
Note: The symmetry of nature w.r.t translation in time means laws of nature do not change with time. The symmetry of nature w.r.t translation in space means laws of nature are the same everywhere in the universe.