Branches of Physics

⦽ Classical Physics
     ⥅ This branch of Physics is mainly concerned with the laws of motion and gravitation as outlined in Isaac Newton and James Maxwell's kinetic theory and thermodynamics, respectively. this branch of physics deals mostly with matter and energy. Often, physics which date before 1900 are considered classical physics, whereas physic which date after 1900 are considered modern physics.
     ⥅ In Classical Physics, energy and matter are considered separate entities. Acoustics, optics, classical mechanics and electromagnetic are traditionally branches within classical physics. Moreover, any theory of physics that is considered null and void in modern physics automatically falls under the realm of classical physics.

THE THREE LAWS OF PHYSICS
1. Law of Inertia: A body remains at rest or in uniform motion in a straight line unless acted upon by a force
2. Force= Mass x Acceleration: A body's rate of change of momentum is proportional to the force causing it.
3. Action= Reaction: When a force acts on a body due to another body, then an equal and opposite force acts simultaneously on that body.

⧬ Modern Physics
      ⥅ Modern Physics is a branch of Physics that is mainly concerned with the theory of relatively and quantum mechanics. Albert Einstein and Max Plank were the pioneers of modern physics as the first scientists to introduce the theory of relativity and quantum mechanics, respectively. In modern physics, energy and matter are not considered as separate entities. Rather, they are considered different forms of each other.

⧬Nuclear Physics
      ⥅Nuclear Physics is a branch of physics that dears with the constituents, structures, behaviour, and interactions of atomic nuclei. This branch of physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons.
      ⥅In the Modern Age, nuclear physics has become very wide in its scope and has been applied in many fields. It is used in power generation, nuclear weapons, imaging, industrial and agricultural isotopes, and more.

WHO DISCOVERED NUCLEAR PHYSICS?
    ⧭ The history of nuclear physics as a distinct field from atomic physics begins with the discovery of radioactivity by Henri Bacquerel in 1896. The discovery of the electron one year later indicated that the atom had an internal structure. With this, studies began on the nuclei of atoms, thus nuclear physics was born.

⧬Atomic Physics
    ⥅Atomic physics is a branch of physics that deals with the composition of the atom apart from the nucleus. It is mainly concerned with the arrangement and behaviour of electrons in the shells around the nucleus. Thus, atomic physics mostly examines electrons, ions, and neutral atoms. One of the earliest steps toward atomic physics was recognizing that all matter is comprised of atoms. the true beginning of atomic physics is marked by the discovery of spectral lines and the attempt to explain them. This resulted in an entirely new understanding of the structure of atoms and how they behave.

⧬Geophysics
    ⥅Geophysics is a branch of physics that deals with the study of the Earth. It is mainly concerned with the shape, structure and composition of the Earth, but geophysicists also study gravitational force, magnetic fields, earthquakes, magma, and more. Geophysics was only recognized as a separate discipline in the 19th century, but its origins date back to ancient times. 
    ⥅All of these discoveries can be included in the field of geophysics, which is defined as:
      ⧪A natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis⧪

⧬ Biophysics
     ⥅ Biophysics studies biological problems and the structure of molecules in living organisms using techniques derived form physics. One of the most groundbreaking achievements of biophysics is the discovery of the structure of DNA by James Watson and Francis Crick.

⧬Mechanical Physics
     ⥅ Mechanical Physics is a branch of physics that deals with the motion of material objects under the influence of forces.

⧬Acoustics 
     ⥅The word "acoustics" is derived from a Greek word akouen, meaning "to hear". Hence, we can define acoustics as a branch of physics that studies how sound is produced, transmitted, received and controlled. Acoustics also deals with the effects of sounds in various mediums.

⧬Optics
     ⥅Optics is a branch of physics that studies electromagnetic radiation like light and infrared radiation, its interactions with matter, and instruments used to gather information due to these interactions. Optics includes the study of sight.

WHO INVENTED OPTICS?
     ⧭Optics began with the creation of lenses by the Ancient Egyptians and Mesopotamians. This was followed up by the theories of light and vision developed by ancient Greek philosophers and the development of geometric optics in the Greco-Roman world.
     ⧭These earlier studies on optics are known as classical optics. Studies that came after the 20th century, such as wave optics and quantum optics, are known as modern optics.

⧬Thermodynamics
     ⥅ Thermodynamics is a branch of physics that deals with heat and temperature and their relation to energy and work. The behaviour of these quantities is governed by the four laws of thermodynamics.

WHO DISCOVERED THERMODYNAMICS?
     ⧭The field of thermodynamics was developed from the work of Nicolas Leonard Sadi Carnot who believed that engine efficiency was the key that could help France win the Napoleonic Wars. The Scottish physicist Lord Kelvin was the first to come up with a concise definition of thermodynamics. His definition stated:
        ⧪Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency⧪

WHAT ARE THE FOUR LAWS OF THERMODYNAMICS?
  ⦽ The four laws of thermodynamics are as follows:
⧫If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This law helps define the concept of temperature.

⧫When energy passes, as work, as heat, or with matter, into or out from a system, the system's internal energy changes in accord with the law of conservation of energy. Equivalently, perpetual motion machines of the first kind (machines that produce work with no energy input) are impossible.

⧫In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases. Equivalently, perpetual motion machines of the second kind (convert thermal energy into mechanical work) are impossible.

⧫The entropy of a system approaches a constant value as the temperature approaches absolute zero. With the exception of non-crystalline solids (glasses), the entropy of a system at absolute zero is typically close to zero, and is equal to the natural logarithm of the product of the quantum ground states.


⧬Astrophysics
     ⥅ The word "astrophysics" is a combination of two Latin-derived words: astro, which means "star,"  and phisis, which means "nature." Thus, astrophysics can be defined as a branch of astronomy which is concerned with the study of universe (stars, galaxies, and planets) using the laws of Physics.

WHAT IS THE DIFFERENCE BETWEEN ASTROPHYSICIST AND AN ASTRONOMER?
     ⧪Technically speaking, astronomers only measure the positions and characteristics of celestial bodies, whereas astrophysicists use the application physics to understand astronomy. However, the terms are now used interchangeably, since all astronomers use physics to conduct their research.