Introduction to Physics: Definition, Branches, Importance and Scholars of Physics

Introduction to Physics

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Physics is defined as the branch of science that studies matter, energy, motion, force and the interactions between them across the universe. It is a natural science that tries to explain how the natural world works, from the motion of a football to the movement of planets. 

Note: Recall that matter is anything that has mass and occupies space (e.g water, air, rock), while energy is the ability to do work (e.g heat, light, sound, electricity).

As the most fundamental physical science, physics seeks to explain everything from subatomic particles and atoms to planets, galaxies, and the cosmos itself.

 

The word physics comes from the Greek word "physis", meaning nature. Physics is a natural science which relies on observation, measurement, and experiment.

Physics is called the "fundamental science" because chemistry, biology, geology, and engineering all rest on its laws.

You can read on the fundamental physics concepts here

 

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The Scientific Method

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Physicists solve problems in a series of steps (known as the scientific method).

The scientific method is a systemic, step-by-step and emperical process used by researchers to explore observations, test ideas, and answer questions about the natural world. They include:

1. Observe a phenomenon

Observation as a scientific approach refers to the active, systematic process of gathering data and information about natural or social phenomena using the human senses or scientific instruments.

Observation can be put into:

• Qualitative Observation: This involves describing properties, characteristics, or qualities that cannot be measured with numbers (e.g., color, odor, texture, or shape).

• Quantitative Observation: This involves collecting numerical data or measurements (e.g., length of 10m, temperature of 100°C, mass of 50kg, or counting 4 specimens in biology lab.).

 

2. State the problem

To state a problem (as a scientific approach) refers to a clear, concise, and evidence-backed statement that identifies a specific knowledge gap, unresolved difficulty, or practical failure in a given context.

Below is an example of a stated problem through scientific approach. 

Lagos is an urbanized city with large population of humans and industries; and the atmosphere is polluted with greenhouse gases.

 

3. Form a hypothesis (an educated guess)

A hypothesis (as a scientific method) is defined as a proposed, educated explanation for an observation or phenomenon that can be tested through experimentation or empirical research.

A hypothesis must be testable (framed) so that an experiment can support it (prove it right), or prove it wrong.

 

4. Test it by experiment

An experiment in the scientific method refers to a structured, empirical procedure used to test a hypothesis, discover cause-and-effect relationships, and verify (confirm) or refute scientific models.

You can read on the concept of heat and temperature here.

 

5. Record and analyse the results.

Recording results (or data collection) in the scientific approach is defined as the systematic, accurate, and unbiased documentation of measurements, observations, or phenomena gathered during an experiment.

The types of result (or data recorded) are grouped into two. These are:

• Quantitative Data: This involves taking numerical measurements such as length (m), mass (kg), time (s), amount of substance (mol), temperature (°C), etc.

• Qualitative Data: These are descriptive, non-numerical observations such as color changes, texture, gas production, or behavioral notes.

 

6. Draw a conclusion

A conclusion in the scientific method is the final decision or judgment made about an experiment's results, determining whether the evidence supports or refutes the original hypothesis.

If the experiment supports the hypothesis, it becomes a scientific law and theory.

A scientific law is a concise statement or mathematical formula that summarizes a consistent, universal pattern or observable occurrence in nature.

A scientific theory is a well-tested, broad, and comprehensive explanation of a natural phenomenon that connects multiple facts, laws, and verified hypotheses.

You can read on gravity and facts on gravity here.

 

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Importance of Physics

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• Technology: Phones, computers, television, radio, and the internet all come from physics.

• Medicine: X-rays, ultrasound scans, MRI, radiotherapy, and thermometers and all made from the laws and principles of physics.

• Engineering and construction: Bridges, buildings, and machines are designed using laws of force and motion.

• Energy and power: Generating and transmitting electricity, solar panels, and nuclear power are made possible through insights on physics.

• Transport:: Cars, trains, aircraft, and ships are products of physics.

• Communication: Satellites, fibre optics, and mobile networks functions as a result of physics research.

• Space exploration: They include devices like rockets, satellites, and telescopes, all made from physics research.

• Foundation for other sciences: Chemistry, biology, geology, and astronomy all use physics since they rest on its laws.

• Everyday understanding: It gives us insight on why ice floats, why we see lightning before hearing thunder, how a lever makes lifting easier, etc.

• Careers like engineering, medicine, aviation, telecommunications, meteorology, teaching, and research require knowledge on physics.

• Weather forecasting and disaster management: Research through physics helps us understand storms, floods, earthquakes and weather forecast.

You can read the concept of velocity and acceleration here.

 

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Branches of Physics

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Classical Physics

Classical physics refers to the collection of physics theories and principles developed before the 20th century. It describes macroscopic and astronomical phenomena through cause-and-effect relationships and metaphysical view that all events within the universe can occur only in one possible way (complete determinism).

The table below show the branches of physics developed before about 1900 (called classical physics)

Branch	What it studies
Mechanics	Motion, forces, and the effects of forces on objects
Heat (Thermodynamics)	Heat, temperature, and energy transfer
Light (Optics)	Behaviour of light: reflection, refraction, lenses, mirrors
Sound (Acoustics)	Production, transmission, and properties of sound
Electricity	Electric charges, current, and circuits
Magnetism	Magnets and magnetic fields
Electromagnetism	The link between electricity and magnetism
Fluid mechanics	Liquids and gases at rest and in motion

 

You can read an introduction to Newton's laws of motion here.

 

Modern Physics

Modern physics refers to post-1900 theories that deal with extreme conditions, such as subatomic (quantum) scales or speeds approaching the speed of light (relativity). It incorporates relative space-time, wave-particle duality, quantized energy packets (quanta), and probabilistic outcomes.

The table below show the branches of physics developed from about 1900 (modern physics)

 

Branch	What it studies
Atomic physics	The structure of the atom and electrons
Nuclear physics	The nucleus, radioactivity, and nuclear energy
Quantum physics	Behaviour of matter at very small scales
Relativity	Space, time, and gravity at very high speeds
Electronics	Devices such as diodes and transistors
Solid-state physics	Properties of solid materials

 

You can read on the concept of density here.

 

Interdisciplinary branches of physics

Interdisciplinary branches of physics refer to physics combined with other fields. It includes the following:

• Astrophysics: Study of the stars, planets, and the universe.

• Geophysics: Study of the Earth (earthquakes, magnetism, and interior).

• Biophysics: Study of physics concerning living things.

• Medical physics: Study of physics in diagnosis and treatment.

• Meteorology: Focuses on weather and atmosphere.

You can read on zeroth law of thermodynamics here.

 

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Scholars in Physics and Their Achievements

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Ancient and early scholars

Name	Years	Nationality	Work
Archimedes	c. 287–212 BC	Greek	Discovered the principle of buoyancy (upthrust) and explained levers and pulleys
Galileo Galilei	1564–1642	Italian	Improved the telescope, discovered the moons of Jupiter, studied the pendulum and falling bodies, and developed the idea of inertia.
Christiaan Huygens	1629–1695	Dutch	Proposed the wave theory of light and improved the pendulum clock
Robert Boyle	1627–1691	Irish	Boyle's law on the pressure and volume of gases

You can read on the importance of gravity here.

 

Founders of classical physics

Name	Years	Nationality	Work
Isaac Newton	1642–1727	English	Three laws of motion, the law of universal gravitation, work on the spectrum of light, and co-development of calculus. His book *Principia* was published in 1687.
Alessandro Volta	1745–1827	Italian	Invented the first electric battery (1800)
Hans Christian Ørsted	1777–1851	Danish	Showed in 1820 that electric current produces a magnetic field.
Georg Ohm	1789–1854	German	Ohm's law, relating voltage, current, and resistance (1827)
Michael Faraday	1791–1867	English	Discovered electromagnetic induction (1831), the principle behind generators and transformers
James Prescott Joule	1818–1889	English	Studied the relationship between heat and work; the unit of energy is named after him.
Lord Kelvin	1824–1907	British.	Developed the absolute (Kelvin) temperature scale
James Clerk Maxwell	1831–1879	Scottish.	Unified electricity, magnetism, and light in his electromagnetic theory
Heinrich Hertz	1857–1894	German	Produced and detected radio waves (1887)

Please read on the concept of heat transfer here.

 

Founders of modern physics

Name	Year	Nationality	Work
Wilhelm Röntgen	1845–1923	German	Discovered X-rays (1895) and won the first Nobel Prize in Physics (1901)
Henri Becquerel	1852–1908	French	Discovered radioactivity (1896)
J.J. Thomson	1856–1940	English	Discovered the electron (1897).
Max Planck	1858–1947	German	Originated quantum theory (1900)
Marie Curie	1867–1934	Polish-French	Discovered polonium and radium; and pioneered research on radioactivity. She won two Nobel Prizes, in Physics (1903) and Chemistry (1911).
Ernest Rutherford	1871–1937	New Zealand-born British	Proposed the nuclear model of the atom (1911)
Albert Einstein	1879–1955	German-born	Theory of relativity, the equation E = mc², and an explanation of the photoelectric effect, for which he won the Nobel Prize (1921).
Niels Bohr	1885–1962	Danish	Proposed the model of the atom with electrons in fixed energy levels (1913).
James Chadwick	1891–1974	English	Discovered the neutron (1932)
Stephen Hawking	1942–2018)	English	Research on black holes and the origin of the universe.

 

Please read the next topic (Measurement in physics; fundamental, derived and supplementary quantities) here.

 

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Practice Questions

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A. Objective Questions

1. The word "physics" comes from the Greek word "physis", meaning _____. A. matter B. nature C. energy D. light

2. Which of these is NOT a branch of physics A. Optics B. Acoustics C. Mechanics D. Botany

3. The scientist who discovered the electron was _____. A. Rutherford B. Bohr C. J.J. Thomson D. Chadwick

4. Electromagnetic induction was discovered by _____. A. Faraday B. Volta C. Ohm D. Joule

5. The branch of physics that studies sound is _____. A. Optics B. Acoustics C. Thermodynamics D. Mechanics

6. Einstein won the Nobel Prize for his explanation of _____. A. relativity B. gravity C. the photoelectric effect D. radioactivity

7. The three laws of motion were formulated by _____. A. Galileo B. Newton C. Archimedes D. Maxwell

8. Which scientist won Nobel Prizes in two different sciences? A. Marie Curie B. Einstein C. Bohr D. Hertz

9. Ultrasound scanning is an application of physics in A. agriculture B. medicine C. transport D. construction

10. The study of the Earth using physical principles is called _____. A. astrophysics B. biophysics C. geophysics D. electronics

11. Who discovered X-rays? A. Becquerel B. Röntgen C. Curie D. Hertz

12. Archimedes is best known for his work on _____.  A. buoyancy B. radioactivity C. the electron D. the neutron

 

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B. Fill in the Blanks

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13. Physics is the study of ______ and ______ and how they interact.

14. The nuclear model of the atom was proposed by ______.

15. The branch of physics dealing with heat is called ______.

16. Radio waves were first produced and detected by ______.

 

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C. Short Answer Questions

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17. Define physics.

18. List any four importance of physics.

19. Name any four branches of physics and state what each studies.

20. Distinguish between classical and modern physics, giving two examples of each.

21. Define (a) matter (b) energy.

 

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D. Theory Questions

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22. (a) Explain the scientific method. (b) Outline the steps a student would use to investigate whether heavier objects fall faster than lighter ones.

23. Discuss five ways in which physics has improved human life.

24. Describe the contributions of any four scientists to the development of physics.

25. Explain the difference between electricity, magnetism, and electromagnetism, and name the scientists linked to each.