Scientists & Inventions is part of Physics. Below are notes on 14 sub-topics, followed by practice MCQs from State PSC and UPSC papers.

Becquerel and Curies' Work on Radioactivity

  • Natural radioactivity was discovered by Henri Becquerel.
  • Artificial radioactivity was discovered by Irène Joliot-Curie and Frédéric Joliot-Curie.

Bohr's Atomic Model and Quantized Energy Levels

Niels Bohr (1913 Atomic Model): 1.

    • Proposed that electrons revolve in specific stable orbits (stationary states) without emitting radiant energy.
    • Stated that electron angular momentum in stable orbits is quantized: `mvr = n(h/2π)`.
    • Energy is emitted/absorbed only when electrons transition between stationary states (quantized energy levels).
    • Awarded Nobel Prize in Physics (1922) for his services in the investigation of the structure of atoms and of the radiation emanating from them. Albert Einstein: Awarded Nobel Prize in 5. Physics (1921) for his discovery of the law of the photoelectric effect. C.V. Raman: 6.
    • Discovered the Raman Effect (scattering of light) on February 28, 1928.
    • Awarded Nobel Prize in Physics (1930) for the Raman Effect.
    • Founded the Raman Research Institute (RRI) in Bengaluru, 1948. Jagadish Chandra Bose (J.C. Bose): Not 4. awarded Nobel Prize in Physics. Satyendra Nath Bose (S.N. Bose): The 5. particle 'Boson' is associated with his name. Murray Gell-Mann: Coined the term 'Quark' 6. for fundamental particles (constituting protons and neutrons). Werner Heisenberg: Proposed the Uncer7. tainty Principle in quantum mechanics. India's National Science Day: 8.
    • Celebrated annually on February 28th.
    • Commemorates the discovery of the Raman Effect.
    • 2024 Official Theme: "Indigenous Technologies for Viksit Bharat".

Chadwick's Discovery of the Neutron

  • Neutron discovered by James Chadwick.
  • Discovery made in 1932.
  • Neutron is an electrically neutral subatomic particle.

Einstein's Theories of Relativity and Photoelectric Effect

  • Albert Einstein: Proposed the Theory of Relativity (Special in 1905, General in 1915); explained the Photoelectric Effect; developed Mass-Energy Equivalence (E=mc²).
  • Einstein's Nobel Prize: Awarded the Nobel Prize in Physics for 1921 (presented in 1922) for his discovery of the law of the photoelectric effect.
  • Einstein's "Annus Mirabilis" (1905): Published seminal papers on the photoelectric effect, Brownian motion, and the special theory of relativity.
  • Photoelectric Effect: Phenomenon where electrons are emitted from a material when light shines upon it; explained by Einstein using the concept of light quanta (photons).
  • Einstein Quote: "Science without Religion is lame and Religion without Science is blind."
  • S. N. Bose: Indian physicist who worked with Einstein, contributing to Bose-Einstein statistics and the concept of Bose-Einstein condensate.
  • Stephen Hawking: Renowned theoretical physicist, known for work on black holes and cosmology; authored 'A Brief History of Time'. Quote: "If you feel you are trapped in a black hole, don't give up. There is a way out."
  • Richard Feynman: Often regarded as the "father of nanotechnology/nanomaterials" for his visionary ideas.
  • M. N. Saha: Outstanding contribution to the principle of thermal ionization (Saha equation).
  • Sir C. V. Raman: Awarded Nobel Prize for his work on the scattering of light (Raman Effect).
  • Louis de Broglie: Proposed the wave nature of electrons.
  • E. O. Lawrence: Invented the Cyclotron.
  • Wilhelm Roentgen: Discovered X-rays; awarded the first Nobel Prize in Physics (1901).
  • Nobel Prize in Physics 2023: Awarded to Pierre Agostini, Ferenc Krausz, and Anne L'Huillier for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter.
  • Nobel Prize in Physics 2022: Awarded to Alain Aspect, John F. Clauser, and Anton Zeilinger for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.
  • Nobel Prize in Physics 2020: Awarded to Roger Penrose, Reinhard Genzel, and Andrea Ghez for discoveries concerning black holes.
  • Nobel Prize in Physics 2016: Awarded to David J. Thouless, F. Duncan M. Haldane, and J. Michael Kosterlitz for theoretical discoveries of topological phase transitions and topological phases of matter.
  • Nobel Prize in Physics 2014: Awarded to Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura for the invention of efficient blue light-emitting diodes (LEDs), which enabled bright and energy-saving white light sources.
  • Special Breakthrough Prize in Fundamental Physics 2017: Awarded to Ronald Drever, Kip S. Thorne, and Rainer Weiss for LIGO and the observation of gravitational waves.

Faraday's Laws of Electromagnetic Induction

  • Oersted's Discovery (1820): Observed that electric current produces a magnetic field (magnetic effect of current).
  • Faraday's Discovery (1831): Discovered electromagnetic induction, demonstrating that changing magnetic fields can induce electric current/EMF.
  • Faraday's First Law: An electromotive force (EMF) is induced in a conductor whenever the magnetic flux linking the conductor changes.
  • Faraday's Second Law: The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux through the circuit. Mathematically: \( \text{EMF} = -N \frac{d\Phi}{dt} \), where \( N \) is the number of turns and \( \Phi \) is the magnetic flux.
  • Lenz's Law: The direction of the induced current or EMF is such that it opposes the change in magnetic flux that produced it (conservation of energy). This is indicated by the negative sign in Faraday's Second Law.
  • Key Principle: Relative motion between a conductor and a magnetic field, or a changing magnetic field, is essential for inducing an EMF.

Galileo's Contributions to Kinematics and Astronomy (Telescope)

  • Galileo Galilei (1564-1642): Italian astronomer, physicist, engineer, and mathematician.
  • Often referred to as the "father of observational astronomy," "father of modern physics," and "father of modern science."
  • Contributions to Kinematics (Study of Motion):
    • Laid the foundations for classical mechanics.
    • First to describe and give scientific consideration to the principle of Inertia.
    • Conducted experiments on falling objects, demonstrating that objects fall at the same rate regardless of their mass (in the absence of air resistance).
    • Studied pendulums and uniform acceleration.
    • Invented an early form of the thermoscope (a precursor to the thermometer).
  • Contributions to Astronomy (Telescope):
    • In 1609, significantly improved the refracting telescope (though he did not invent the first telescope, he greatly enhanced its design and optical power).
    • First to use the telescope for systematic astronomical observations.
    • Key Astronomical Discoveries using the telescope:
      • Discovered the four largest moons of Jupiter (Io, Europa, Ganymede, Callisto), now known as the Galilean moons. This provided strong evidence against the geocentric model.
      • Observed the phases of Venus, supporting the heliocentric model.
      • Discovered mountains and craters on the Moon, indicating it was not a perfect sphere.
      • Observed sunspots.
      • Resolved the Milky Way into individual stars.
    • Strongly advocated for and provided observational evidence supporting the Copernican (heliocentric) model of the solar system.

Invention of the Laser and its Principles

  • LASER stands for Light Amplification by Stimulated Emission of Radiation.
  • Core principle: Stimulated Emission, theorized by Albert Einstein (1917).
  • Key pioneers in maser/laser theory: Charles H. Townes and Arthur Schawlow.
  • First working laser: Theodore Maiman (1960), utilizing a ruby crystal.
  • Indian scientist C.K.N. Patel is renowned for his work in photonics and laser technology, notably the invention of the high-power carbon dioxide (CO2) laser.
  • The 2018 Nobel Prize in Physics was awarded to Arthur Ashkin, Gérard Mourou, and Donna Strickland for pioneering inventions in laser physics (optical tweezers and chirped pulse amplification).
  • The 2022 Nobel Prize in Physics was awarded to Alain Aspect, John F. Clauser, and Anton Zeilinger for experiments with entangled photons, pioneering quantum information science (quantum entanglement).
  • The 2014 Nobel Prize in Physics was awarded to Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura for the invention of efficient blue light-emitting diodes (LEDs).

J.J. Thomson's Discovery of the Electron

  • Electron was discovered by Joseph John Thomson.
  • J.J. Thomson determined the charge-to-mass ratio (e/m) of the electron.
  • The elementary charge of an electron (e) was first successfully determined by Robert Millikan (Millikan's oil drop experiment).

Maxwell's Equations of Electromagnetism

  • James Clerk Maxwell (1831-1879) was a Scottish mathematician and physicist.
  • Maxwell's Equations are a set of four partial differential equations that describe the behavior of electric and magnetic fields and their interactions.
  • He unified electricity, magnetism, and optics into a single comprehensive theory of electromagnetism.
  • A key prediction from Maxwell's Equations was the existence of electromagnetic waves.
  • Maxwell demonstrated that light is an electromagnetic wave, propagating at a specific speed in a vacuum.
  • He introduced the concept of "displacement current" to Ampere's Law, completing the set of equations.

Newton's Laws of Motion and Universal Gravitation

  • Isaac Newton: Propounded Laws of Motion and Laws of Universal Gravitational Force in the 17th century.
  • Newton's work on laws of motion and gravitation was published in Philosophiæ Naturalis Principia Mathematica (1687).
  • Isaac Newton was the first to use a glass prism to obtain the spectrum of sunlight.
  • Nobel Prize in Physics for Gravitational Waves (2017): Rainer Weiss, Kip Thorne, Barry Barish.
  • Nobel Prize in Physics (2020): Roger Penrose (black hole formation), Reinhard Genzel and Andrea Ghez (discovery of a supermassive compact object at the Milky Way's center).
  • A Brief History of Time: Authored by Stephen Hawking.
  • The word "atom" was coined by Democritus.
  • Srinivasa Ramanujan (1887-1920): Renowned Indian mathematician.
  • Boson: Class of particles obeying Bose-Einstein statistics; term coined by Paul Dirac, named after Satyendra Nath Bose.
  • Key Inventions/Discoveries:
    • Penicillin: Alexander Fleming.
    • Steam Engine: James Watt.
    • Telephone: Graham Bell.
    • Television: John Baird.

Ohm's Law and Volta's Electric Battery

  • Ohm's Law:
  • Propounded by: Georg Simon Ohm (1827).
  • Statement: The current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) between them, provided temperature and other physical conditions remain constant.
  • Formula: V = IR.
  • Unit of Resistance: Ohm (Ω).
  • Volta's Electric Battery:
  • Inventor: Alessandro Volta (1800).
  • Invention: The Voltaic Pile (first true electric battery).
  • Principle: Utilized chemical reactions between dissimilar metals (e.g., zinc and copper) separated by an electrolyte (brinesoaked cardboard) to generate a continuous electric current.
  • Significance: Provided the first stable and continuous source of electric current, enabling further electrical experimentation and development.

Planck's Quantum Hypothesis and Blackbody Radiation

  • Max Planck (1858-1947): German theoretical physicist.
  • Quantum Hypothesis (1900): Proposed that energy is not emitted or absorbed continuously, but in discrete packets called quanta.
  • Energy of a Quantum: E = hν (where 'h' is Planck's constant, 'ν' is frequency).
  • Blackbody Radiation: Planck's hypothesis provided the first successful explanation for the observed spectrum of blackbody radiation, resolving the "ultraviolet catastrophe" of classical physics.
  • Transition to Modern Physics: Planck's work and the quantum hypothesis are considered the origin of quantum mechanics, marking a fundamental shift from classical to modern physics.
  • Thermodynamic Probability (W): Represents the number of microstates corresponding to a given macrostate.
  • Equilibrium State: In an equilibrium state, the system is in the macrostate with the maximum thermodynamic probability (W), which corresponds to maximum entropy (S = k ln W).

Röntgen's Discovery of X-rays and Medical Applications

  • Wilhelm Conrad Röntgen (W. Roentgen) discovered X-rays.
  • Röntgen is credited with inventing the X-ray machine.
  • X-rays are primarily used in medical applications for diagnostic imaging.
  • Godfrey Hounsfield invented the CT scan (Computerized Tomography), which utilizes X-ray technology for detailed cross-sectional images.

Rutherford's Model of the Atom and Nuclear Structure

  • Ernest Rutherford: Known as the 'Father of Nuclear Physics'.
  • Ernest Rutherford: Discovered the atomic nucleus (via the gold foil experiment).
  • Ernest Rutherford: Identified the proton as a fundamental particle within the nucleus.
  • Alpha (α) particles: Used by E. Rutherford in the gold foil experiment; identified as helium nuclei.
  • Subrahmanyan Chandrasekhar: India-born physicist, awarded Nobel Prize for research on the structure and evolution of stars (e.g., Chandrasekhar Limit).
  • "Chandra" X-ray telescope: Named in honour of Subrahmanyan Chandrasekhar.
  • Meghnad Saha: Indian astrophysicist, known for contributions to thermodynamics and astrophysics (Saha ionization equation).
  • Dr. Raja Ramanna: Prominent Indian nuclear physicist.
  • Henry Cavendish: Discovered hydrogen.
  • Takaaki Kajita (Japan) and Arthur B. McDonald (Canada): Awarded 2015 Nobel Prize in Physics for the discovery of neutrino oscillations.

17. Miscellaneous

Practice MCQs: Scientists & Inventions

Becquerel and Curies' Work on Radioactivity

  1. The phenomenon of radioactivity was first discovered by

    Asked in: UPSC Geoscientist 2023

    1. Marie Curie
    2. Henri Becquerel
    3. Frederick Soddy
    4. Ernest Rutherford
    Show answer

    Answer: B. Henri Becquerel

    B. protects the transmission line against direct lightning stroke C. supresses high frequency oscillation in the line D. reflects back the travelling wave approaching it Ans: A GS&EI ElectEngg 14 2024 1601-2025 Lightning arresters are protective devices that divert excess voltage surges to the ground, thus safeguarding equipment connected to the power system. They act as a switch that closes at a high voltage and opens when the surge has passed.

  2. A lightning arrester connected between the line and earth in a power system

    Asked in: GS&EI ElectEngg 14 2024 1601 2025

    1. protects the terminal equipment against travelling surges
    2. protects the transmission line against direct lightning stroke
    3. suppresses high frequency oscillation in the line
    4. reflects back the travelling wave approaching it
    Show answer

    Answer: A. protects the terminal equipment against travelling surges

    A lightning arrester's primary function is to protect terminal equipment from voltage surges by providing a safe path to earth for surge currents. Henri Becquerel's accidental discovery of radiation from uranium marked the beginning of the study of radioactivity.

  3. Natural radioactivity was discovered by

    Asked in: WBPSC CS Prelims 2020

    1. Marie Curie
    2. Ernest Rutherford
    3. Henri Becquerel
    4. Enrico Fermi
    Show answer

    Answer: C. Henri Becquerel

    In 1896, Henri Becquerel accidentally discovered radioactivity while studying the phosphorescence of uranium salts. He found that the uranium salts emitted radiation that could expose photographic plates even in the dark, indicating an inherent property of the material itself.

  4. Who is not a Nobel Prize winner among the following scientists?

    Asked in: UPPSC Upper Mains 2006

    1. Har Govind Khurana
    2. C.V. Raman
    3. S. Chandrasekhar
    4. Jagdish Chandra Bose
    Show answer

    Answer: D. Jagdish Chandra Bose

    - C.V. Raman won the Nobel Prize in Physics in 1930 for his work on the scattering of light (Raman effect). - Har Gobind Khorana shared the Nobel Prize in Physiology or Medicine in 1968 for his work on the interpretation of the genetic code and its function in protein synthesis. - S. Chandrasekhar shared the Nobel Prize in Physics in 1983 for his theoretical studies of the physical processes important to the structure and evolution of the stars. - Jagdish Chandra Bose (1858-1937) was a pioneering polymath who made significant contributions to physics (radio and microwave optics), botany, and biology. Despite his groundbreaking work, he was not awarded a Nobel Prize.

  5. Match List-I (Inventions) with List-II (Inventors) and select the correct answer from the code given below - List-I List-II 1. I. Curie & F. Joli‐ (A) Cosmic rays ot (B) X-rays 2. Victor Hess (C) Radioactivity 3. W.C. Roentgen (D) Artificial radioactiv‐ 4. Henri Becquerel ity Code -

    Asked in: ADDITIONAL PRIVATE SECRETARY EXAM 2023

    1. A-(4), B-(3), C-(1), D-(2)
    2. A-(2), B-(3), C-(4), D-(1)
    3. A-(2), B-(4), C-(1), D-(3)
    4. A-(1), B-(3), C-(2), D-(4)
    Show answer

    Answer: B. A-(2), B-(3), C-(4), D-(1)

    This question tests knowledge of scientific discoveries and their discoverers. It requires accurate matching of inventions to inventors.

  6. Who was the inventor of Radioactivity ?

    Asked in: Chief Fire Officer Exam 2021

    1. Irene Curie
    2. Rutherford
    3. Marie Curie
    4. Henry Bacquerel
    Show answer

    Answer: D. Henry Bacquerel

    Henri Becquerel is credited with the discovery of radioactivity.

  7. Radio activity was discovered by

    Asked in: Management Officer Exam 2011

    1. Madam Curie
    2. Jenner
    3. Becquerel
    4. Einstein
    Show answer

    Answer: C. Becquerel

    Henri Becquerel discovered radioactivity in 1896.

Bohr's Atomic Model and Quantized Energy Levels

  1. Which of the following scientists was not awarded Noble prize in Physics ?

    Asked in: MPSC CS Prelims 2012

    1. Niel Bohr
    2. Einstein
    3. Jagdishchandra Bose
    4. C. V. Raman
    Show answer

    Answer: C. Jagdishchandra Bose

    Niel Bohr was awarded the Nobel Prize in Physics in 1922. Albert Einstein was awarded the Nobel Prize in Physics in 1921. C. V. Raman was awarded the Nobel Prize in Physics in 1930. Sir Jagdish Chandra Bose was a pioneering Indian scientist known for contributions to radio waves and plant physiology, but he was not awarded a Nobel Prize in Physics.

  2. Which one of the following scientists mentioned that an electron in an atom could revolve in certain stable orbits without the emission of radiant energy ?

    Asked in: UPSC NDA 1 2024

    1. Ernest Rutherford
    2. J.J. Thomson
    3. Niels Bohr
    4. Albert Einstein
    Show answer

    Answer: C. Niels Bohr

    - Rutherford's model suggested electrons orbit the nucleus but didn't explain atomic stability. - Classical physics predicted orbiting electrons would radiate energy and spiral into the nucleus. - Niels Bohr proposed quantized orbits where electrons do not radiate energy, leading to stable atoms.

  3. Raman Research Institute is located at X, India and was founded by Y in 1948. X and Y are respectively :

    Asked in: TSPSC Group 1 Prelims 2024

    1. Bengaluru, C.V. Raman
    2. Bengaluru, Vikram Sarabhai
    3. Trivandrum, C.V. Raman
    4. Trivandrum, Vikram Sarabhai
    Show answer

    Answer: A. Bengaluru, C.V. Raman

    - The Raman Research Institute (RRI) is a premier research institute in India. - It is located in Bengaluru (Bangalore). - It was founded by the Nobel laureate physicist Sir C.V. Raman in 1948, shortly after India gained independence. - Sir C.V. Raman initiated research activities at the institute after his retirement from the Indian Institute of Science.

  4. Consider the following statements related to India's National Science Day :

    Asked in: TSPSC Group 1 Prelims 2024

    1. It is celebrated every year on February 28th.
    2. It commemorates the day of the an‐ nouncement of the discovery of the Raman Effect.
    3. The official theme for the year 2024 was "Global Science for Global Well‐ being".
    4. The official theme for the year 2024 was "Indigenous Technologies for Viksit Bharat". Which of the above statements are correct ? A. B, C and D only B. A, B and D only C. A and C only D. A, C and D only
    Show answer

    Answer: B. It commemorates the day of the an‐ nouncement of the discovery of the Raman Effect.

    - Statement A is correct: National Science Day is celebrated every year on February 28th in India. - Statement B is correct: The date February 28th was chosen to commemorate the discovery of the Raman Effect by Indian physicist Sir C.V. Raman in 1928, for which he was awarded the Nobel Prize in Physics in 1930. - Statement C is incorrect: The theme "Global Science for Global Wellbeing" was the theme for National Science Day in 2023. - Statement D is correct: The official theme for National Science Day in 2024 was "Indigenous Technologies for Viksit Bharat".

  5. The name of the particle 'Boson' is associated with the name of

    Asked in: UPSC CAPF 2011

    1. J.C. Bose
    2. S.N. Bose
    3. Isaac Newton
    4. Albert Einstein
    Show answer

    Answer: B. S.N. Bose

    The term 'Boson' is named after the Indian physicist Satyendra Nath Bose (S.N. Bose) for his work on quantum statistics, which laid the foundation for describing the behavior of these particles.

  6. Who among the following has coined the term 'Quark', the fundamental particles that make up protons and neutrons in an atomic nucleus ?

    Asked in: UPSC CAPF 2017

    1. Richard Feynman
    2. Murray Gell-Mann
    3. Albert Einstein
    4. Niels Bohr
    Show answer

    Answer: B. Murray Gell-Mann

    Murray Gell-Mann proposed the quark model and named these fundamental particles 'quarks'.

  7. Uncertainty relation in quantum mechanics was proposed by

    Asked in: WBCS Main Paper 4 2021

    1. Rutherford
    2. Bohr
    3. Heisenberg
    4. Feynman
    Show answer

    Answer: C. Heisenberg

    - The uncertainty principle is a key concept in quantum mechanics. - It deals with the limits of precision in simultaneously measuring conjugate variables like position and momentum.

Chadwick's Discovery of the Neutron

  1. Which of the following pairs of physical phenomenon and the discoverer is/are correctly matched ? 1. James Chadwick : Photoelectric effect 2. Albert Einstein : Neutron 3. Marie Curie : Radium Select the correct answer using the code given below :

    Asked in: UPSC NDA 1 2021

    1. 1, 2 and 3
    2. 1 and 2 only
    3. 2 and 3 only
    4. 3 only
    Show answer

    Answer: D. 3 only

    - James Chadwick discovered the neutron in 1932. The photoelectric effect was explained by Albert Einstein in 1905, building on observations by Heinrich Hertz. - Albert Einstein is famous for his theory of relativity and his explanation of the photoelectric effect, not the discovery of the neutron. - Marie Curie, along with her husband Pierre Curie, discovered the elements polonium and radium in 1898.

  2. Neutrons were discovered by

    Asked in: UPSC NDA 2 2020

    1. James Chadwick
    2. Ernest Rutherford
    3. J. J. Thomson
    4. John Dalton
    Show answer

    Answer: A. James Chadwick

    The discovery of the neutron completed the basic understanding of the composition of the atomic nucleus, alongside protons.

  3. Neutron was discovered by

    Asked in: ae 2024 · District Statistical Officer Assistant Director 2025

    1. Priestley
    2. Rutherford
    3. J.J. Thomson
    4. Chadwick
    Show answer

    Answer: D. Chadwick

    James Chadwick, an English physicist, discovered the neutron in 1932. This discovery was crucial in understanding atomic structure and paved the way for nuclear physics.

Einstein's Theories of Relativity and Photoelectric Effect

  1. Who won the Nobel Prize in Physics for the discovery of the law of photoelectric effect?

    Asked in: APSC CCE Prelims Exam 2020

    1. Wilhelm Roentgen
    2. Albert Einstein
    3. Isaac Newton
    4. Ernest Rutherford
    Show answer

    Answer: B. Albert Einstein

    The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Einstein's explanation involved the idea that light energy is quantized into discrete packets called photons.

  2. Einstein got the Nobel Prize for

    Asked in: BPSC Prelims Exam 64th

    1. relativity
    2. Bose-Einstein condensation
    3. mass-energy equivalence
    4. photoelectric effect
    Show answer

    Answer: D. photoelectric effect

    Albert Einstein was awarded the Nobel Prize in Physics in 1921 (awarded in 1922) for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect. This work, published in 1905, provided crucial evidence for the quantum nature of light.

  3. The 'theory of relativity' is presented by which scientist?

    Asked in: BPSC Prelims Exam 67th Re Exam

    1. Isaac Newton
    2. Stephen Hawking
    3. Marie Curie
    4. Albert Einstein
    Show answer

    Answer: D. Albert Einstein

    Albert Einstein is credited with developing the theory of relativity, which comprises two main parts: special relativity (1905) and general relativity (1915). These theories revolutionized our understanding of space, time, gravity, and the universe.

  4. Who among the following is not a recipient of the Nobel Prize in Physics in 2022?

    Asked in: UPSC CDS 1 2023

    1. Alain Aspect
    2. John F. Clauser
    3. Klaus Hasselmann
    4. Anton Zeilinger
    Show answer

    Answer: C. Klaus Hasselmann

    Alain Aspect, John F. Clauser, and Anton Zeilinger received the 2022 Nobel Prize in Physics for their experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.

  5. Consider the following statement: "If you feel you are trapped in a black hole, don't give up. There is a way out." Who among the following made the above statement?

    Asked in: UPSC CDS 2 2016

    1. Albert Einstein
    2. Stephen Hawking
    3. C. V. Raman
    4. Abdus Salam
    Show answer

    Answer: B. Stephen Hawking

    - Stephen Hawking was a theoretical physicist and cosmologist known for his groundbreaking work on black holes and the origin of the universe. - Despite his severe physical disability (ALS), he continued his scientific research and public engagement throughout his life. - This particular quote reflects his scientific understanding of black holes and can also be interpreted metaphorically about facing difficulties in life.

  6. The Nobel Prize in Physics for the year 2016 was given to

    Asked in: UPSC CDS 2 2017

    1. David J. Thouless
    2. F. Duncan M. Haldane
    3. J. Michael Kosterlitz
    4. All of them
    Show answer

    Answer: D. All of them

    The prize was awarded for their theoretical discoveries of topological phase transitions and topological phases of matter, which have opened the door to an unknown world where matter can assume strange states.

  7. Nobel Prize for Physics for the year 2014 was given to which invention ?

    Asked in: CGPSC Prelims Exam 2014

    1. Red LED
    2. Green LED
    3. White LED
    4. Yellow LED
    Show answer

    Answer: C. White LED

    The Nobel Prize in Physics in 2014 was awarded to Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura for the invention of efficient blue light- emitting diodes (LEDs). The development of blue LEDs was a crucial step that enabled the creation of bright and energy-saving white light sources, making them essential for modern lighting technology. While the award was specifically for the invention of blue LEDs, the key outcome and widely recognized application is the enablement of white LEDs for general lighting.

Faraday's Laws of Electromagnetic Induction

  1. Magnetic effect of current was discovered by

    Asked in: WBCS Main Paper 4 2023

    1. Faraday
    2. Oersted
    3. Ampere
    4. Bohr
    Show answer

    Answer: B. Oersted

    Hans Christian Oersted discovered in 1820 that an electric current creates a magnetic field. This fundamental discovery established a connection between electricity and magnetism.

Galileo's Contributions to Kinematics and Astronomy (Telescope)

  1. Consider the following pairs of scientists and discoveries : Scientists Discoveries (i) Copernicus : Law of gravitation (ii) Kepler : Laws of planetary motion (iii) Galileo : Moons of Jupiter (iv) Newton : Heliocentric theory Select the correctly matched pairs using the codes given below.

    Asked in: APSC CCE Prelims Exam 2023

    1. (i) and (ii) only
    2. (i), (ii) and (iii) only
    3. (i), (ii), (iii) and (iv)
    4. (ii) and (iii) only
    Show answer

    Answer: D. (ii) and (iii) only

    - Copernicus proposed the heliocentric model of the solar system. - Johannes Kepler derived his laws of planetary motion from Tycho Brahe's observational data. - Galileo's telescopic observations supported the heliocentric model and included the discovery of Jupiter's moons, phases of Venus, and craters on the moon. - Isaac Newton developed the laws of motion and the law of universal gravitation, providing the physical explanation for Kepler's laws.

  2. The fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by

    Asked in: UPSC CDS 1 2017

    1. Galileo
    2. Martin Luther
    3. Johannes Kepler
    4. Copernicus
    Show answer

    Answer: C. Johannes Kepler

    - Nicolaus Copernicus proposed the heliocentric model where planets orbit the Sun, but he assumed the orbits were perfect circles. - Galileo Galilei provided telescopic observations that supported the heliocentric model but did not discover elliptical orbits. - Johannes Kepler, using the detailed astronomical data collected by Tycho Brahe, formulated his three laws of planetary motion between 1609 and 1619. - Kepler's First Law states that the orbit of a planet is an ellipse with the Sun at one of the two foci.

  3. Who among the following is known to be the first one to consider the role of inertia in motion?

    Asked in: UPSC Geoscientist 2022

    1. Galileo Galilei
    2. Isaac Newton
    3. Albert Einstein
    4. Nicolaus Copernicus
    Show answer

    Answer: A. Galileo Galilei

    - Inertia is the property of matter resisting changes in motion. - Galileo's work challenged Aristotelian physics regarding motion. - Galileo's experiments and thought experiments led him to the concept of inertia. - Newton later formalized inertia as his First Law of Motion.

  4. Which scientist proposed the theory that the sun is at the centre of our solar system ?

    Asked in: MPSC CS Prelims 2012

    1. Copernicus
    2. Newton
    3. Galileo
    4. Rutherford
    Show answer

    Answer: A. Copernicus

    Nicolaus Copernicus (1473-1543) proposed the heliocentric model of the solar system, placing the Sun at the center with the planets orbiting around it, challenging the prevailing geocentric model.

  5. Which one among the following statements is not correct?

    Asked in: UPSC CISF AC EXE 2018

    1. Johannes Kepler proved that the path of each planet around the Sun is elliptical with the Sun at its focus.
    2. The first successful attempt to establish the size of the Earth is credited to Eratosthenes.
    3. The first Greek to profess a Sun-centred or Heliocentric Universe was Sir Isaac Newton.
    4. The famous astronomical book Almagest was compiled by Ptolemy.
    Show answer

    Answer: C. The first Greek to profess a Sun-centred or Heliocentric Universe was Sir Isaac Newton.

    Statement A is correct. Johannes Kepler formulated his laws of planetary motion in the early 17th century, including the first law stating that planets orbit the Sun in elliptical paths with the Sun at one focus. Statement B is correct. Eratosthenes of Cyrene, a Greek scholar in the 3rd century BC, is famous for making the first relatively accurate calculation of the Earth's circumference using geometry and astronomical observations. Statement C is incorrect. The first known Greek astronomer to propose a heliocentric model of the solar system was Aristarchus of Samos in the 3rd century BC, predating Kepler and Newton by over a thousand years. Sir Isaac Newton (1643-1727) was a British physicist and mathematician, not Greek, and his work explained why planetary orbits are elliptical (gravity), building upon Kepler's descriptive laws. Statement D is correct. The Almagest is the 2nd- century AD astronomical treatise by Claudius Ptolemy, which presented a detailed geocentric model of the universe that remained the standard view for centuries.

  6. Telescope was invented by

    Asked in: UPPCS Prelims 1994

    1. Gallileo
    2. Gutinberg
    3. Edision
    4. Graham Bell
    Show answer

    Answer: A. Gallileo

    Hans Lippershey, Zacharias Janssen, and Jacob Metius are credited with inventing the first telescopes around 1608. However, Galileo Galilei quickly built his own versions, significantly improving the magnification and clarity, and turned his telescope towards the sky in 1609, making groundbreaking astronomical discoveries (like the moons of Jupiter, phases of Venus, and sunspots). In the context of popular science history, Galileo is often associated strongly with the invention and popularization of the telescope for scientific use.

  7. gas engine was invented by :

    Asked in: UPPCS Prelims 1995

    1. Diesel
    2. Davy
    3. Daimler
    4. charles
    Show answer

    Answer: C. Daimler

    Gottlieb Daimler was a pioneer in the development of high-speed internal combustion engines that made automobiles possible.

Invention of the Laser and its Principles

  1. The Nobel Prize for Physics in 2018 was awarded for pioneering work in which field?

    Asked in: HAS Prelims 2019

    1. Laser Physics
    2. Quantum Mechanics
    3. Thermodynamics
    4. Aerodynamics
    Show answer

    Answer: A. Laser Physics

    - The Nobel Prize in Physics 2018 was awarded jointly to Arthur Ashkin (USA), Gérard Mourou (France), and Donna Strickland (Canada). - Arthur Ashkin received half of the prize for his invention of optical tweezers and their application to biological systems. - Gérard Mourou and Donna Strickland shared the other half for their method of generating high-intensity, ultra-short optical pulses, known as Chirped Pulse Amplification (CPA). - Both optical tweezers and CPA are significant breakthroughs in the field of laser physics.

  2. Which of the following pairs is NOT correctly matched? Indian Scientists : Field of Work/Research

    Asked in: TNPSC CS Prelims 2014

    1. C.K.N. Patel : Photonics and Laser
    2. Meghnad Saha : Astrophysics
    3. Benjamin Peary Pal : Disease resistant varieties of wheat
    4. Autar Singh Paintal : Cosmology and relativity
    Show answer

    Answer: D. Autar Singh Paintal : Cosmology and relativity

    - C.K.N. Patel is a physicist and electrical engineer, known for inventing the CO2 laser and contributions to photonics. - Meghnad Saha was an astrophysicist famous for his ionization equation (Saha equation). - Benjamin Peary Pal was an acclaimed plant breeder and geneticist who developed several disease-resistant varieties of wheat and roses.

  3. The Nobel Prize in Physics in 2022 was awarded for :

    Asked in: UPSC CISF AC EXE 2023

    1. Evolution of Universe
    2. Quantum entanglement
    3. Black hole
    4. Laser Physics
    Show answer

    Answer: B. Quantum entanglement

    The Nobel Prize in Physics in 2022 was awarded jointly to Alain Aspect, John F. Clauser, and Anton Zeilinger for "experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science." This work is directly related to quantum entanglement, a phenomenon where two or more particles are linked in such a way that they cannot be described independently of each other, even when separated by large distances.

  4. 2014 Nobel award in Physics is associated with the invention of which type of LED?

    Asked in: WBPSC CS Prelims 2015

    1. Blue
    2. Green
    3. Red
    4. Yellow
    Show answer

    Answer: A. Blue

    The invention of the blue LED was a significant breakthrough because it enabled the creation of white light sources by combining blue light with yellow phosphors, or by mixing red, green, and blue light. Red and green LEDs had been developed much earlier, but a blue LED was necessary to achieve energy-efficient white lighting and color displays.

J.J. Thomson's Discovery of the Electron

  1. Electron was discovered by

    Asked in: UPSC CISF AC EXE 2017 · WBCS Main Paper 4 2021

    1. Michael Faraday
    2. Joseph John Thomson
    3. Henry Cavendish
    4. Earnest Rutherford
    Show answer

    Answer: B. Joseph John Thomson

    J.J. Thomson discovered the electron in 1897 through his experiments with cathode ray tubes, determining that cathode rays were composed of negatively charged particles much smaller than atoms.

  2. Who, for the first time, successfully determined the charge of an electron ?

    Asked in: ASCO 2014

    1. Thomson
    2. Millikan
    3. Rutherford
    4. Coulomb
    Show answer

    Answer: B. Millikan

    HORTICULTURE DEVELOPMENT OF‐ FICER(HDO) -2015 J.J. Thomson discovered the electron and measured its charge-to-mass ratio. However, it was Robert Millikan's oil-drop experiment (around 1909) that accurately measured the magnitude of the elementary electric charge, the charge of a single electron.

  3. Who, for the first time, successfully determined the charge of an electron? - [A] Thompson - [B] Millikan - [C] Rutherford - [D] Coulomb

    Asked in: HORTICULTURE DEVELOPMENT OF‐ FICER(HDO) 2015 · POST GRADUATE TEACHER (PGT) 2018

    1. Thompson
    2. Millikan
    3. Rutherford
    4. Coulomb
    Show answer

    Answer: B. Millikan

    Robert Millikan, in his famous oil-drop experiment conducted between 1909 and 1913, successfully measured the elementary electric charge, which is the charge of an electron.

  4. Mark the wrong combination :

    Asked in: Group C Exam 2011

    1. James Watt : Steam Engine
    2. A.G. Bell : Telephone
    3. J.L. Baird : Television
    4. J. Perkins : Penicillin
    Show answer

    Answer: D. J. Perkins : Penicillin

    The question asks to identify the wrong combination. The inventor of Penicillin is incorrectly matched with J. Perkins.

  5. Who, for the first time, successfully determined the charge of an electron ?

    Asked in: POST GRADUATE TEACHER (PGT) 2018

    1. Thomson
    2. Millikan
    3. Rutherford
    4. Coulomb
    Show answer

    Answer: B. Millikan

    Millikan's experiment was crucial in establishing the quantization of electric charge.

Maxwell's Equations of Electromagnetism

  1. Light is an electromagnetic wave, is the principle of

    Asked in: ASO 2025

    1. Michael Faraday
    2. Isaac Newton
    3. Oersted
    4. James Clarke Maxwell
    Show answer

    Answer: D. James Clarke Maxwell

    This question tests knowledge of fundamental principles in physics, specifically electromagnetism and optics, and the scientists associated with these discoveries.

Newton's Laws of Motion and Universal Gravitation

  1. The science best-seller *A Brief History of Time* which made it into the Guinness Book of Records was written by :

    Asked in: HAS Prelims 2019

    1. Stephen Hawking
    2. Isaac Asimov
    3. H. G. Wells
    4. Stephen King
    Show answer

    Answer: A. Stephen Hawking

    A Brief History of Time: From the Big Bang to Black Holes is a seminal popular science book about cosmology written by British physicist Stephen Hawking. The book was a massive international bestseller and was listed in the Guinness Book of Records for staying on the Sunday Times bestseller list for a record-breaking 237 weeks.

  2. In which century (A.D.) did Issac Newton put forth his three laws of motion ?

    Asked in: MPSC CS Prelims 2012

    1. 16th century
    2. 17th century
    3. 18th century
    4. 19th century
    Show answer

    Answer: B. 17th century

    The year 1687 falls within the 17th century. A century spans 100 years; the 17th century covers the years 1601 through 1700.

  3. Name the scientist who first used a glass prism to obtain the spectrum of sunlight

    Asked in: UPSC NDA 2 2020

    1. C. V. Raman
    2. Lord Rayleigh
    3. Isaac Newton
    4. S. Chandrasekhar
    Show answer

    Answer: C. Isaac Newton

    Newton's experiments with prisms laid the foundation for the understanding of the dispersion of light and the nature of color.

  4. Three US Scientists have been awarded the Nobel prize in Physics for their work on gravitational waves. Which of the following is not one of them ?

    Asked in: OPSC CS Prelims 2017

    1. Rainer Weiss
    2. Kip Thorne
    3. Barry Barish
    4. Jay Hannigam
    Show answer

    Answer: D. Jay Hannigam

    These three scientists played leading roles in the Laser Interferometer Gravitational-Wave Observatory (LIGO) collaboration, which made the first detection of gravitational waves in September 2015, confirming a prediction made by Albert Einstein a hundred years earlier.

  5. Who invented the law of motion?

    Asked in: Headmaster (Secondary School) 2018

    1. Friedrich
    2. Newton
    3. Addison
    4. Alexander
    Show answer

    Answer: B. Newton

    Sir Isaac Newton formulated the laws of motion.

  6. Who is not the Nobel Prize 2020 winner in Physics?

    Asked in: acf 2019

    1. Roger Penrose
    2. Reinhard Genzel
    3. Andrea Ghez
    4. Jennifer Doudna
    Show answer

    Answer: D. Jennifer Doudna

    Jennifer Doudna won the Nobel Prize in Chemistry in 2020, not Physics.

  7. Who coined the word "atom" ?

    Asked in: ASO 2025

    1. E. Rutherford
    2. Democritus
    3. John Dalton
    4. Thomson
    Show answer

    Answer: B. Democritus

    Democritus is credited with originating the concept of the atom as the smallest, indivisible unit of matter. While his ideas were philosophical, they laid the groundwork for later scientific atomic theories.

Ohm's Law and Volta's Electric Battery

  1. Who amongst the following is a pioneer in discovering the heating effect of electric current ?

    Asked in: UPSC CDS 1 2021

    1. Isaac Newton
    2. Galileo Galilei
    3. James P. Joule
    4. J.J. Thomson
    Show answer

    Answer: C. James P. Joule

    James P. Joule's experiments demonstrated the relationship between electric current flow through a resistor and the heat generated, leading to Joule's Law of Heating.

  2. Equal volume of all gases, when measured at the same temperature and pressure, contain an equal number of particles. Who proposed the above law ?

    Asked in: UPSC NDA 1 2023

    1. Charles
    2. Boyle
    3. Avogadro
    4. Lussac
    Show answer

    Answer: C. Avogadro

    Avogadro's Law relates the volume of a gas to the number of particles (molecules or atoms) under constant temperature and pressure conditions.

Planck's Quantum Hypothesis and Blackbody Radiation

  1. Whose theory brought in a transition from classical physics to modern physics ?

    Asked in: MPSC CS Prelims 2012

    1. Issac Newton
    2. C. V. Raman
    3. H. J. Bhabha
    4. Max Planck
    Show answer

    Answer: D. Max Planck

    Max Planck's formulation of quantum theory in 1900, proposing that energy is quantized, marked a fundamental departure from classical physics and is considered the beginning of modern physics.

  2. In the equilibrium state, thermodynamic probability of system is

    Asked in: Group C Exam 2011

    1. $\infty$
    2. one
    3. zero
    4. minimum
    Show answer

    Answer: B. one

    This question relates to statistical thermodynamics and the concept of equilibrium. Thermodynamic probability, also known as the multiplicity or number of microstates corresponding to a macrostate, is a measure of how likely a particular macrostate is.

Röntgen's Discovery of X-rays and Medical Applications

  1. We use CFL to save electrical energy and to provide sufficient light. The full form of CFL is

    Asked in: UPSC NDA 1 2015

    1. Condensed filament light
    2. Compact filament lamp
    3. Condensed fluorescent lamp
    4. Compact fluorescent lamp
    Show answer

    Answer: D. Compact fluorescent lamp

    The acronym CFL stands for Compact Fluorescent Lamp. These lamps are designed to be smaller and more energy-efficient than traditional linear fluorescent lamps, allowing them to fit into the same fixtures as incandescent bulbs.

  2. Which of the following was invented by Wilhelm Roentgen?

    Asked in: UPPCS Prelims 2018

    1. Radio
    2. X-Ray Machine
    3. Electric Bulb
    4. None of the above
    Show answer

    Answer: B. X-Ray Machine

    Wilhelm Roentgen was awarded the first Nobel Prize in Physics in 1901 for his discovery of X-rays.

  3. Wilhelm Roentgern invented

    Asked in: UPPCS Prelims 2005

    1. Radio
    2. X-Ray Machine
    3. Electric Bulb
    4. Electric Motor
    Show answer

    Answer: B. X-Ray Machine

    Wilhelm Conrad Röntgen (or Roentgen) was a German physicist who is credited with discovering X- rays in 1895. This discovery led to the development and use of the X-ray machine, which revolutionized medical diagnostics.

  4. Which of the following pairs is correctly matched?

    Asked in: UPPCS Prelims 2004

    1. Reinhold Messner: Computer Technology
    2. Harlow Shapley: Astronomy
    3. Gregor Mendel: Hereditary Theory
    4. Godfrey Hounsfield: CT scan
    Show answer

    Answer: C. Gregor Mendel: Hereditary Theory

    Gregor Mendel conducted experiments in the 19th century that demonstrated particulate inheritance, where traits are passed down through discrete units (now known as genes), laying the groundwork for the field of genetics and hereditary theory.

  5. Who invented X-rays?

    Asked in: District Library and Information Officer(DLIO) 2018

    1. A. G. Bell
    2. Madame Curie
    3. Roentgen
    4. Hicks
    Show answer

    Answer: C. Roentgen

    The discovery of X-rays by Wilhelm Conrad Roentgen was a groundbreaking event in the field of physics and medicine.

  6. The scientist who invented X-rays is A) W. Roentgen B) Willian Harvey C) Alexander Wood D) Lewis E. Waterman

    Asked in: Inspector(Legal Metrology & Consumer Affairs) 2020

    1. W. Roentgen
    2. Willian Harvey
    3. Alexander Wood
    4. Lewis E. Waterman
    Show answer

    Answer: A. W. Roentgen

    Wilhelm Conrad Röntgen is credited with the discovery of X-rays, a groundbreaking scientific achievement that revolutionized medical diagnostics.

Rutherford's Model of the Atom and Nuclear Structure

  1. Match the names of scientists in Column I with their fundamental given in Column II and select the correct answer using the options given below the columns : Column I Column II a. splitting of the atom and 1. Louis Pasteur discovery of proton 2. Alexander b. discovery of X-Rays Fleming 3. Ernest Rutherc. enzyme lysozyme and ford benzylpenicillin 4. William Konrad d. vaccination and microbi‐ Roentgen al fermentation

    Asked in: HAS Prelims 2019

    1. 1-c, 2-d, 3-a, 4-b
    2. 1-d, 2-a, 3-b, 4-c
    3. 1-a, 2-c, 3-d, 4-b
    4. 1-b, 2-a, 3-c, 4-d
    Show answer

    Answer: A. 1-c, 2-d, 3-a, 4-b

    The scientifically correct pairings are Louis Pasteur with vaccination and microbial fermentation, Alexander Fleming with enzyme lysozyme and benzylpenicillin, Ernest Rutherford with splitting of the atom and discovery of the proton (specifically, his work on nuclear transmutation and naming the proton), and William Konrad Roentgen with the discovery of X-Rays. Option A incorrectly pairs Pasteur with Fleming's work (c) and Fleming with Pasteur's work (d), but correctly pairs Rutherford with his work (a) and Roentgen with his work (b). This indicates a probable error in the options as presented in the source question.

  2. To which India-born physicist a Nobel Prize was awarded for his research related to the structure and evolution of stars ?

    Asked in: MPSC CS Prelims 2012

    1. C. V. Raman
    2. Amartya Sen
    3. Meghnad Saha
    4. S. Chandrashekar
    Show answer

    Answer: D. S. Chandrashekar

    Subrahmanyan Chandrasekhar, an India-born astrophysicist who spent most of his career in the US, was awarded the Nobel Prize in Physics in 1983 for his theoretical studies of the physical processes of importance to the structure and evolution of stars, particularly the Chandrasekhar limit for white dwarfs.

  3. α-particles were discovered by

    Asked in: MPSC CS Prelims 2015

    1. J.J. Thomson
    2. A. Einstein
    3. E. Rutherford
    4. Madam Curie
    Show answer

    Answer: C. E. Rutherford

    Ernest Rutherford, through his experiments, particularly the gold foil experiment, identified and characterized alpha (α) particles as positively charged particles emitted during radioactive decay. He later identified them as the nuclei of helium atoms.

  4. Who among the following is known as the Father of Nuclear Physics ?

    Asked in: UPSC CISF AC EXE 2021

    1. E. Rutherford
    2. J.J. Thomson
    3. Niels Bohr
    4. James Chadwick
    Show answer

    Answer: A. E. Rutherford

    Rutherford's work revolutionized the understanding of atomic structure and radioactivity. J.J. Thomson discovered the electron. Niels Bohr developed an early model of the atom based on quantum mechanics. James Chadwick discovered the neutron.

  5. T. Kajita and A. Mc Donald, winner of year 2015 Nobel Prize for Physics belong to which of the following countries respectively?

    Asked in: UPPCS Prelims 2016

    1. U.S.A. and Japan
    2. Japan and U.S.A.
    3. Japan and Canada
    4. Canada and U.S.A.
    Show answer

    Answer: C. Japan and Canada

    Takaaki Kajita is a Japanese physicist who won the Nobel Prize in Physics in 2015. Arthur B. McDonald is a Canadian physicist who shared the prize with Kajita. They were awarded for their work demonstrating that neutrinos change identities, which proves that neutrinos have mass.

  6. Match the names of outstanding Indian scientists given in List I with area of their specialised work given in List II and select the correct answer using the codes given below the lists: List I List II I. Dr. Raja A) Plant Chemistry Ramanna II. Dr. M.S. Swam‐ B) Nuclear Physics inathan C) Thermodynamics and III. Prof. U.R. Rao astrophysics IV. Prof. Meghnad D) Space research Saha E) Agricultural sciences Codes:

    Asked in: UPPCS Prelims 1998

    1. I-C, II-E, III-B, IV-A
    2. I-B, II-A, III-D, IV-C
    3. I-B, II-E, III-D, IV-C
    4. I-C, II-A, III-D, IV-B
    Show answer

    Answer: C. I-B, II-E, III-D, IV-C

    This question requires matching prominent Indian scientists with their specialized areas of work. I. Dr. Raja Ramanna was a renowned Indian nuclear physicist and played a key role in India's nuclear weapons program. His area is Nuclear Physics (B). II. Dr. M.S. Swaminathan is an agricultural scientist globally recognized as a leader of the Green Revolution in India. His area is Agricultural sciences (E). III. Prof. U.R. Rao was a distinguished space scientist, former Chairman of ISRO, and significantly contributed to satellite technology and space exploration. His area is Space research (D). IV. Prof. Meghnad Saha was a famous astrophysicist known for developing the Saha ionization equation, fundamental in astrophysics. His area is Thermodynamics and astrophysics (C). Matching these gives: I-B, II-E, III-D, IV-C.

  7. Who is the scientist in whose honour the “Chandra” X-ray telescope has been named?

    Asked in: UPPCS Prelims 2001

    1. Chandrasekhar Venkat Raman
    2. Jagdish Chandra Bose
    3. Prafulla Chandra Roy
    4. Subrahmanyan Chandrasekhar
    Show answer

    Answer: D. Subrahmanyan Chandrasekhar

    The Chandra X-ray Observatory, a space telescope launched by NASA, is named in honor of the distinguished Indian-American astrophysicist Subrahmanyan Chandrasekhar (often known simply as Chandra). He was awarded the Nobel Prize in Physics in 1983 for his theoretical studies of the physical processes of importance to the structure and evolution of the stars. His work included the theoretical maximum mass for a white dwarf star (now known as the Chandrasekhar limit), which is crucial for understanding stellar evolution and the formation of black holes.