Intro to Physics[class-12]part=1

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Science and its origin

Science is a systematic understanding of natural phenomena in detail so that it can be predicted, controlled and modified. Science involves exploring, experimenting and speculating phenomena happening around us.

• The word Science is derived from a latin verb Scientia meaning ‘to know’.
• Scientific method is a way to gain knowledge in a systematic and in-depth way. It involves:
  • Systematic observations
  • Controlled experiments
  • Qualitative and Quantitative reasoning
  • Mathematical modeling
  • Prediction and verification (or falsification) of theories
  • Speculation or Prediction
• Science does not have any final theory. The improved observations, accurate tools keep improving the knowledge and perspective. Johannes Kepler used Tycho Brahe’s research on planetary motion to improve Nicolas Copernicus theory
• Natural Sciences
  Natural science is a branch of science concerned with the description, prediction, and understanding of natural phenomena, based on observational and empirical evidence. It consists of following disciplines:
  • Physics
  • Chemistry
  • Biology
  
• Physics
  Physics is a study of basic laws of nature and their manifestation in different natural phenomena. Physics is the study of physical world and matter and its motion through space and time, along with related concepts such as energy and force.
  • Word Physics is derived from a Greek word phusikḗ meaning nature.
  • Two principal types of approaches in Physics are:
    • Unification: 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.
    • 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).
  Impactand uses of Physics
  • It can explain a phenomena happening over a large magnitude with a simple theory.
  • Experiments and observations are used to develop new theories for unidentified phenomena and improve old theories for existing phenomena.
  • Development of devices using laws of physics.
  • Scope of Physics
    Scope of Physics is vast as it covers quantities with length magnitude as high as 1040m or more (astronomical studies of universe) and as low as 10-14m or less (study of electrons, protons etc). Similarly the range of time scale goes from 10-22s to 1018s and mass from 10-30kg to 1055kg.
    Physics is broadly divided into two types based on its scope - Classical Physicsand Modern Physics. Classical physics deal with the macroscopic phenomena while the modern physics deals with the microscopic phenomena.
    
    
    
  • Macroscopic Domain
    Macroscopic domain includes phenomena at large scales like laboratory, terrestrial and astronomical. It includes following subjects:
    • Mechanics – 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. Examples,
      • Propulsion of rocket by ejecting gases
      • Water/Sound waves
      • Equilibrium of bent rod under a load
    
    • Electrodynamics – It deals with electric and magnetic phenomena associated with charged and magnetic bodies. Examples,
      • motion of a current-carrying conductor in a magnetic field
      • the response of a circuit to an ac voltage (signal)
      • the propagation of radio waves in the ionosphere
    
    • Optics – It deals with phenomena involving light. Examples,
      • Reflection and refraction of light
      • Dispersion of light through a prism
      • Colour exhibited by thin films
    
    • Thermodynamics – It deals with systems in macroscopic equilibrium and changes in internal energy, temperature, entropy etc. of systems under application of external force or heat. Examples,
      • 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.
    
    
    
  • 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.
     
    Hypothesis, Axiom and Models
    Hypothesis -is a supposition without assuming that it is true. It may not be proved but can be verified through a series of experiments.
    Axiom- is a self-evident truth that it is accepted without controversy or question.
    Model -is a theory proposed to explain observed phenomena.
    Assumption- is the basis of physics, where a number of phenomena can be explained. These assumptions are made from experiments, observation and a lot of statistical data.
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