Physics Scientists & Their Discoveries

Why This Chapter Matters

Open any SSC CGL, CHSL, MTS, or RRB NTPC paper from the last five years and you will find at least one question that simply asks "who discovered X" or "the SI unit of Y is named after which scientist." This is the single highest-return topic in the whole physics syllabus, because it needs zero calculation and rewards pure recall. Two to four marks come from this chapter alone in most General Science sections, and it repeats every single year with barely any variation in the names asked.

Here is the shape of what's coming: a working list of scientists mapped to their discoveries, laws, and the units named after them, followed by a short, honest look at the Nobel Prize in Physics facts connected to India, and a table of physical constants that carry a scientist's name. The single biggest mistake aspirants make with this chapter is mixing up scientists who share a surname initial or worked in the same field — Faraday and Franklin, Volta and Volt (the unit is named after Volta, not the other way round), Rutherford and Bohr, Curie and Becquerel. Exam-setters know this confusion exists and design questions to exploit it. You will see call-outs through this chapter flagging exactly these traps.

Mechanics: The Foundational Names

Isaac Newton gave physics its backbone. His three laws of motion explain everything from why a bus jerks you forward when it brakes to why a rocket needs to expel gas to move. He also gave us the universal law of gravitation, explaining why an apple falls and why the Moon does not fly off into space. The SI unit of force, the newton (N), carries his name, and so does the branch of mechanics itself, often called "Newtonian mechanics."

Analogy: think of Newton's first law like a passenger asleep on a bus seat with no seatbelt. The bus stops suddenly, the passenger keeps moving forward, not because a force pushed them forward, but because nothing stopped their motion in time. That is inertia in one sentence, and it is exactly the kind of scenario SSC loves to frame as a "why does this happen" question.

Archimedes, working nearly two thousand years before Newton, gave us Archimedes' Principle: a body immersed in a fluid experiences an upward buoyant force equal to the weight of fluid displaced. This is why a massive steel ship floats while a small steel nail sinks — the ship's shape displaces enough water to generate a buoyant force greater than its weight, while the nail's shape does not. The story of Archimedes shouting "Eureka" while stepping into an overflowing bath is folklore, but the principle behind it is rock solid exam material.

Exam trap: Archimedes' principle is about buoyant force from displaced fluid. Do not confuse it with Pascal's law, which is about pressure transmission, not buoyancy.

Blaise Pascal showed that pressure applied to an enclosed fluid is transmitted equally in all directions. This is Pascal's law, and it is the working principle behind hydraulic lifts and hydraulic brakes in cars and buses. The SI unit of pressure, the pascal (Pa), is named after him.

Galileo Galilei studied falling bodies and showed that, ignoring air resistance, all objects fall at the same rate regardless of mass. He also studied the pendulum and improved the telescope enough to observe Jupiter's moons, which supported the idea that not everything orbits Earth. Galileo is often called the father of modern observational astronomy and experimental physics.

Johannes Kepler worked out three laws describing how planets move around the Sun in elliptical orbits, with speed varying depending on distance from the Sun. Newton later used Kepler's laws as a stepping stone to derive the law of gravitation itself. Keep Kepler and Newton separate in your head: Kepler described how planets move, Newton explained why.

Daniel Bernoulli showed that as the speed of a moving fluid increases, its pressure decreases. This single idea, Bernoulli's principle, explains why an aircraft wing generates lift and why a shower curtain gets pulled inward when the water is running fast. Robert Boyle and Jacques Charles gave us the basic gas laws: Boyle's law links pressure and volume at constant temperature, Charles's law links volume and temperature at constant pressure. Both are foundational for the kinetic theory of gases questions you will see later in this book.

Electricity and Magnetism: The Most Tested Cluster

This is the single most exam-heavy section of this chapter, so read it twice.

Michael Faraday discovered electromagnetic induction — that a changing magnetic field can generate an electric current in a nearby conductor. This one discovery is the working principle behind every electric generator on the planet. He also formulated the laws of electrolysis. The SI unit of capacitance, the farad (F), honours him.

Alessandro Volta invented the voltaic pile, the first true chemical battery capable of producing a continuous electric current, replacing earlier one-shot devices. The SI unit of electric potential difference, the volt (V), is named after him.

Exam trap: Volt is named after Volta, not "Volt" as a surname. This sounds obvious written down, but under exam pressure, students confuse the unit's spelling with a person's actual name and pick wrong options in matching-type questions.

Georg Simon Ohm established the relationship between voltage, current, and resistance in a conductor, known today as Ohm's law (V = IR). The unit of electrical resistance, the ohm (Ω), is named after him.

André-Marie Ampère did foundational work connecting electricity and magnetism, showing that current-carrying wires exert force on each other. The SI base unit of electric current, the ampere (A), carries his name, and it remains one of the seven base units you studied in Chapter 2.

James Prescott Joule studied the relationship between heat and mechanical work, giving us Joule's law of heating. The SI unit of energy and work, the joule (J), is named after him.

James Clerk Maxwell unified electricity, magnetism, and light into a single set of equations, predicting the existence of electromagnetic waves that travel at the speed of light. This theoretical prediction was later confirmed experimentally by Heinrich Hertz, whose name lives on in the SI unit of frequency, the hertz (Hz).

Nikola Tesla developed practical alternating current (AC) systems and the AC induction motor, which is why long-distance electricity transmission across India runs on AC rather than DC — AC voltage can be stepped up and down efficiently using transformers, cutting transmission losses over long lines. The SI unit of magnetic flux density, the tesla (T), honours him.

Charles-Augustin de Coulomb formulated Coulomb's law, describing the force between two electric charges — mathematically similar in form to Newton's law of gravitation, but for charges instead of masses. The unit of electric charge, the coulomb (C), is named after him.

Memory hook: for the electricity unit-to-scientist pairs, think "FAVOOJHTC" as a chain: Faraday-farad, Ampère-ampere, Volta-volt, Ohm-ohm, Oersted (magnetic field around a wire, unit oersted), Joule-joule, Hertz-hertz, Tesla-tesla, Coulomb-coulomb. Each pair is a scientist whose surname became the unit for the exact quantity they discovered or defined. Walk through the chain once before your exam and every pairing question in this cluster becomes a formality.

Hans Christian Oersted discovered, almost by accident during a lecture demonstration, that an electric current produces a magnetic field around a wire — the first experimental link between electricity and magnetism, and the discovery that set Faraday and Ampère's later work in motion.

Joseph Henry independently discovered electromagnetic induction around the same time as Faraday, and the SI unit of inductance, the henry (H), is named after him, not Faraday, even though the two men worked on closely related phenomena.

Exam trap: students often assign the unit "henry" to Faraday because both worked on induction. Faraday gets the farad (capacitance); Henry gets the henry (inductance). Keep the quantities straight, not just the names.

Heat, Light, and Sound

William Thomson, better known as Lord Kelvin, defined the absolute temperature scale that starts at absolute zero. The SI unit of temperature, the kelvin (K), is named after him, and it is the only SI unit written without a degree symbol.

Anders Celsius gave us the Celsius temperature scale used across India and most of the world, while Daniel Gabriel Fahrenheit gave us the Fahrenheit scale still used in the United States, and he was also the first to build a reliable mercury-in-glass thermometer.

Christiaan Huygens proposed that light travels as a wave, a theory that competed for over a century with Newton's rival idea that light is made of particles. Both turned out to be partly right — light shows both wave and particle behaviour, a fact confirmed decisively only in the twentieth century.

Evangelista Torricelli, a student of Galileo, invented the mercury barometer and demonstrated the existence of atmospheric pressure, explaining why a column of mercury stays suspended in a sealed tube against the vacuum above it.

Christian Doppler explained why the pitch of a sound changes as its source moves toward or away from you — the Doppler effect — the same physics behind the change in siren pitch as an ambulance passes you on the road, and the principle used in radar guns that measure vehicle speed.

Real-world grounding: next time you hear a train horn shift pitch as it rushes past a level crossing, that shift is the Doppler effect happening in real time. It is not a coincidence that this exact scenario shows up in SSC questions almost every cycle — examiners like physics that a student can verify from memory of daily life.

Modern Physics: Atoms, Radioactivity, and Relativity

J.J. Thomson discovered the electron in 1897, the first subatomic particle ever identified, using a cathode ray tube experiment. Ernest Rutherford later discovered the proton and, through his famous gold foil experiment, proposed the nuclear model of the atom, showing that an atom is mostly empty space with a dense, positively charged nucleus at its centre. James Chadwick, a student of Rutherford, discovered the neutron in 1932, completing the basic subatomic particle picture taught at school level.

Niels Bohr refined Rutherford's model by proposing that electrons occupy fixed energy levels or shells around the nucleus, and can jump between levels by absorbing or emitting energy. This Bohr model is still the version taught at the fact-recall level for competitive exams, even though quantum mechanics later refined it further.

Henri Becquerel discovered radioactivity in 1896, almost by accident, when he found that uranium salts fogged a photographic plate even without exposure to light. The SI unit of radioactivity, the becquerel (Bq), is named after him.

Marie Curie, working with her husband Pierre Curie, extended Becquerel's discovery and identified two new radioactive elements, polonium (named after her homeland Poland) and radium. Marie Curie remains the only person in history to win Nobel Prizes in two different sciences — Physics in 1903 and Chemistry in 1911. The non-SI unit of radioactivity, the curie (Ci), is named after the Curies.

Exam trap: Becquerel discovered radioactivity itself; the Curies isolated new radioactive elements from it. Both are Nobel-linked, both have units named after them, and SSC questions frequently swap their roles to test whether you actually know the distinction.

Wilhelm Röntgen discovered X-rays in 1895, and for this he received the very first Nobel Prize in Physics ever awarded, in 1901. X-rays are used today in medical imaging and airport security scanning, both grounded in the same basic property Röntgen observed: these rays pass through soft tissue but are blocked by denser material like bone or metal.

Max Planck founded quantum theory, proposing that energy is emitted and absorbed in discrete packets called quanta rather than continuously. Planck's constant (h) is one of the most fundamental constants in all of physics.

Albert Einstein explained the photoelectric effect — how light striking a metal surface can eject electrons — using Planck's quantum idea, and this work, not his more famous relativity theory, is what won him the 1921 Nobel Prize in Physics. Einstein also gave the world the theory of relativity and the mass-energy equivalence relation E = mc², showing that mass and energy are two forms of the same underlying quantity.

Memory hook: for the atomic-model sequence, remember "Diamonds Take Real Beautiful Colours" — Dalton (solid indivisible sphere), Thomson (plum pudding, electron), Rutherford (nucleus), Bohr (energy shells), Chadwick (neutron). This is the historical order in which the atomic model evolved, and SSC loves to test that order directly.

Nobel Prize in Physics — India-Linked Facts (Brief)

You do not need the full Nobel Physics list for this exam, but two names come up repeatedly and deserve to be locked in.

Chandrasekhara Venkata Raman (C.V. Raman) won the Nobel Prize in Physics in 1930 for discovering the Raman effect, the scattering of light where a small fraction of scattered light changes wavelength when it passes through a transparent medium. Raman remains the only person to win a Nobel Prize in the sciences while working entirely in India, as an Indian citizen, and the discovery itself was made in Kolkata. National Science Day is celebrated on 28 February every year in India to mark the day Raman announced this discovery in 1928.

Subrahmanyan Chandrasekhar, Raman's nephew, won the Nobel Prize in Physics in 1983 for his theoretical work on the structure and evolution of stars, including the Chandrasekhar limit, which defines the maximum mass a white dwarf star can have before it collapses further. He conducted this Nobel-winning work as a US-based scientist of Indian origin.

One more name worth knowing even though he never won the Nobel Prize: Satyendra Nath Bose, whose work with Einstein led to Bose-Einstein statistics, and the class of particles called bosons — including the famous "Higgs boson" — is named after him. Many exam aspirants assume Bose won a Nobel Prize because a fundamental particle bears his name; he did not, and this exact misconception shows up as a distractor option in MCQs.

(For the fuller list of Indian and India-linked Nobel laureates across all categories, refer to the Static GK Compendium's dedicated Nobel Prize chapter — this book keeps the coverage physics-specific and brief on purpose.)

Physical Constants Named After Scientists

Competitive exams sometimes ask which constant is associated with which scientist, without expecting you to know the numerical value. The table below covers what actually gets asked.

Constant	Named after	What it represents
Gravitational constant (G)	Associated with Newton's law; first measured accurately by Henry Cavendish	Strength of gravitational attraction between two masses
Planck's constant (h)	Max Planck	Links a photon's energy to its frequency
Boltzmann constant (k)	Ludwig Boltzmann	Links average kinetic energy of particles to temperature
Avogadro's number (NA)	Amedeo Avogadro	Number of particles in one mole of a substance
Rydberg constant	Johannes Rydberg	Used in calculating spectral lines of hydrogen atom
Stefan-Boltzmann constant	Josef Stefan and Ludwig Boltzmann	Links a black body's temperature to radiated energy

Exam trap: the gravitational constant G is often wrongly attributed directly to Newton in casual references. Newton formulated the law; Cavendish first measured G's value experimentally, decades after Newton's death. If a question asks specifically "who first measured the value of G," the answer is Cavendish, not Newton.

SI Units Named After Scientists — Consolidated View

You met most of these individually above. Seeing them together, organised by the quantity they measure, is what actually sticks before an exam.

Quantity	SI unit	Named after
Force	newton (N)	Isaac Newton
Pressure	pascal (Pa)	Blaise Pascal
Energy, work, heat	joule (J)	James Prescott Joule
Power	watt (W)	James Watt
Electric current	ampere (A)	André-Marie Ampère
Electric potential	volt (V)	Alessandro Volta
Electric resistance	ohm (Ω)	Georg Simon Ohm
Electric charge	coulomb (C)	Charles-Augustin de Coulomb
Capacitance	farad (F)	Michael Faraday
Inductance	henry (H)	Joseph Henry
Magnetic flux density	tesla (T)	Nikola Tesla
Magnetic flux	weber (Wb)	Wilhelm Weber
Frequency	hertz (Hz)	Heinrich Hertz
Temperature	kelvin (K)	Lord Kelvin (William Thomson)
Radioactivity (SI)	becquerel (Bq)	Henri Becquerel
Radioactivity (non-SI, still asked)	curie (Ci)	Marie and Pierre Curie

James Watt, whose name completes this table, did not invent the steam engine outright but improved it dramatically, making it efficient enough to power the machinery of the Industrial Revolution. The SI unit of power, the watt (W), honours him, and it is worth remembering that a 100-watt bulb and a 100-watt fan consume energy at the exact same rate, just doing different work with it.

Two More Names Worth Knowing

Guglielmo Marconi is credited with the practical development of long-distance wireless telegraphy (radio transmission), work that eventually won him a share of the 1909 Nobel Prize in Physics. Thomas Alva Edison did not invent the light bulb from a blank slate — earlier inventors had built working versions — but he engineered a commercially practical, long-lasting incandescent bulb and built the systems needed to actually distribute electricity to homes, which is why he is remembered as the one who "gave the world electric light."

Exam trap: questions sometimes ask "who invented the light bulb" expecting Edison as the answer, and other times specifically ask "who first demonstrated an incandescent lamp," where earlier names like Humphry Davy or Joseph Swan are the technically correct answer. If a question uses the word "invented" plainly with no other qualifier, Edison is the safe SSC-standard answer; treat it as the accepted exam narrative rather than a strict history-of-science claim.

Quick Revision — One-Line Facts

• Newton gave the three laws of motion and the law of gravitation; unit of force is the newton.
• Archimedes' principle explains buoyancy: upward force equals weight of fluid displaced.
• Pascal's law explains hydraulic brakes and lifts; unit of pressure is the pascal.
• Galileo showed all falling bodies accelerate equally, ignoring air resistance.
• Kepler described planetary orbits as ellipses, not perfect circles.
• Bernoulli's principle explains why aircraft wings generate lift.
• Boyle's law links pressure and volume at constant temperature; Charles's law links volume and temperature at constant pressure.
• Faraday discovered electromagnetic induction; unit of capacitance is the farad.
• Volta invented the first chemical battery; unit of potential difference is the volt.
• Ohm gave the law V = IR; unit of resistance is the ohm.
• Ampère is honoured with the SI base unit of current, the ampere.
• Joule linked heat and mechanical work; unit of energy is the joule.
• Maxwell unified electricity, magnetism, and light into one theory.
• Hertz confirmed electromagnetic waves exist; unit of frequency is the hertz.
• Tesla developed practical AC systems; unit of magnetic flux density is the tesla.
• Coulomb's law governs force between electric charges; unit of charge is the coulomb.
• Oersted first showed current produces a magnetic field.
• Henry gave the unit of inductance, distinct from Faraday's farad.
• Kelvin defined the absolute temperature scale starting at absolute zero.
• Torricelli invented the mercury barometer, proving atmospheric pressure exists.
• Doppler effect explains the pitch change of a passing train horn or ambulance siren.
• J.J. Thomson discovered the electron; Rutherford discovered the proton and the nucleus; Chadwick discovered the neutron.
• Bohr proposed electrons occupy fixed energy shells around the nucleus.
• Becquerel discovered radioactivity; unit of radioactivity (SI) is the becquerel.
• Marie and Pierre Curie discovered polonium and radium; non-SI radioactivity unit is the curie.
• Röntgen discovered X-rays and won the first-ever Nobel Prize in Physics, 1901.
• Planck founded quantum theory; Planck's constant is named after him.
• Einstein won the 1921 Nobel Prize in Physics for the photoelectric effect, not relativity.
• C.V. Raman won the 1930 Nobel Prize in Physics for the Raman effect, discovered in Kolkata.
• National Science Day is celebrated on 28 February to mark Raman's discovery.
• S.N. Bose never won a Nobel Prize despite the boson particle class being named after him.
• Cavendish first measured the value of the gravitational constant G, not Newton.
• James Watt improved the steam engine; unit of power is the watt.

Memory Tables

Table 1: Scientist to Discovery/Law

Scientist	Key discovery or law
Isaac Newton	Laws of motion, law of gravitation
Archimedes	Principle of buoyancy
Blaise Pascal	Law of pressure transmission
Michael Faraday	Electromagnetic induction, laws of electrolysis
Georg Simon Ohm	Ohm's law (V = IR)
J.J. Thomson	Discovery of the electron
Ernest Rutherford	Nuclear model of the atom, discovery of proton
James Chadwick	Discovery of the neutron
Niels Bohr	Energy-shell model of the atom
Henri Becquerel	Discovery of radioactivity
Marie and Pierre Curie	Discovery of polonium and radium
Wilhelm Röntgen	Discovery of X-rays
Max Planck	Quantum theory
Albert Einstein	Photoelectric effect, theory of relativity
C.V. Raman	Raman effect (scattering of light)
S. Chandrasekhar	Chandrasekhar limit (stellar structure)

Table 2: Unit to Scientist Ready-Reference

SI unit	Quantity measured	Scientist honoured
newton	Force	Isaac Newton
pascal	Pressure	Blaise Pascal
joule	Energy/work	James Prescott Joule
watt	Power	James Watt
ampere	Electric current	André-Marie Ampère
volt	Electric potential	Alessandro Volta
ohm	Electric resistance	Georg Simon Ohm
coulomb	Electric charge	Charles-Augustin de Coulomb
farad	Capacitance	Michael Faraday
henry	Inductance	Joseph Henry
tesla	Magnetic flux density	Nikola Tesla
weber	Magnetic flux	Wilhelm Weber
hertz	Frequency	Heinrich Hertz
kelvin	Temperature	Lord Kelvin
becquerel	Radioactivity (SI)	Henri Becquerel
curie	Radioactivity (non-SI)	Marie and Pierre Curie

Practice MCQs

Q1. The SI unit of force is named after which scientist? (a) James Watt (b) Isaac Newton (c) Blaise Pascal (d) Michael Faraday

Q2. Archimedes' Principle is most directly used to explain which everyday phenomenon? (a) Why a ship floats (b) Why a bulb glows (c) Why a compass points north (d) Why sound travels through water

Q3. Who invented the first true chemical battery, the voltaic pile? (a) Ampère (b) Volta (c) Ohm (d) Faraday

Q4. The unit "farad" is named after which scientist, for which quantity? (a) Newton, for force (b) Faraday, for capacitance (c) Henry, for inductance (d) Ohm, for resistance

Q5. Which law explains the working of hydraulic brakes in a bus? (a) Ohm's law (b) Pascal's law (c) Boyle's law (d) Faraday's law

Q6. Who discovered electromagnetic induction, the working principle of the electric generator? (a) Nikola Tesla (b) Michael Faraday (c) James Watt (d) Alessandro Volta

Q7. Which scientist discovered the electron? (a) Ernest Rutherford (b) Niels Bohr (c) J.J. Thomson (d) James Chadwick

Q8. Who discovered the neutron, completing the basic subatomic particle model? (a) J.J. Thomson (b) James Chadwick (c) Ernest Rutherford (d) Henri Becquerel

Q9. C.V. Raman won the Nobel Prize in Physics in 1930 for discovering: (a) X-rays (b) The Raman effect (c) The electron (d) Radioactivity

Q10. Which Indian-origin scientist won the Nobel Prize in Physics in 1983 for work on the structure and evolution of stars? (a) S.N. Bose (b) Homi Bhabha (c) S. Chandrasekhar (d) C.V. Raman

Q11. Albert Einstein's 1921 Nobel Prize in Physics was awarded specifically for his work on: (a) The theory of relativity (b) Mass-energy equivalence (c) The photoelectric effect (d) Quantum entanglement

Q12. Which scientist first measured the actual numerical value of the gravitational constant G? (a) Isaac Newton (b) Henry Cavendish (c) Johannes Kepler (d) Galileo Galilei

Q13. The SI unit of inductance, the henry, is named after Joseph Henry and not after Michael Faraday, even though both worked on related phenomena. What did Faraday's own named unit, the farad, come to measure instead? (a) Magnetic flux (b) Capacitance (c) Inductance (d) Resistance

Q14. Marie Curie remains the only person in history to win Nobel Prizes in two different sciences. What were the two fields? (a) Physics and Medicine (b) Chemistry and Medicine (c) Physics and Chemistry (d) Physics and Literature

Q15. Satyendra Nath Bose is honoured through the naming of which class of fundamental particles, even though he never won a Nobel Prize himself? (a) Fermions (b) Bosons (c) Quarks (d) Neutrinos

Answer Key

Q	Answer	Reason
Q1	(b)	Newton formulated the laws of motion and gravitation; the SI unit of force carries his name.
Q2	(a)	Buoyant force equal to displaced fluid weight is why large steel ships float despite their mass.
Q3	(b)	Volta built the first device producing continuous electric current, unlike earlier one-shot electrical devices.
Q4	(b)	Farad measures capacitance; do not confuse it with henry, which measures inductance.
Q5	(b)	Pascal's law states pressure applied to an enclosed fluid transmits equally in all directions, powering hydraulic brakes.
Q6	(b)	Faraday's discovery of electromagnetic induction is the direct working principle behind every electric generator.
Q7	(c)	Thomson identified the electron using cathode ray tube experiments in 1897, the first subatomic particle found.
Q8	(b)	Chadwick, a student of Rutherford, discovered the neutron in 1932, completing the proton-neutron-electron picture.
Q9	(b)	The Raman effect is the change in wavelength of scattered light, discovered by Raman in Kolkata in 1928.
Q10	(c)	Chandrasekhar, Raman's nephew, won for the Chandrasekhar limit describing maximum white dwarf star mass.
Q11	(c)	Einstein's Nobel citation specifically credits the photoelectric effect explanation, not his more famous relativity work.
Q12	(b)	Newton formulated the law of gravitation; Cavendish experimentally measured G's value decades later.
Q13	(b)	Farad measures capacitance, the ability of a component to store electric charge, distinct from inductance.
Q14	(c)	Curie won Physics in 1903 and Chemistry in 1911, a feat no one else has matched across the sciences.
Q15	(b)	Bosons, including the Higgs boson, are named after Bose despite him never receiving a Nobel Prize.