Quiz of the Day
Atoms, Quanta & Physics Pioneers
Wednesday, 7 October 2026
Marking Niels Bohr's birthday (Oct 7, 1885) — a quiz on atomic structure, quantum physics, and the famous physicists who unraveled the subatomic world
1. Danish physicist Niels Bohr, born October 7, 1885, is best known for his 1913 model of what?
- The atom
- The universe
- The solar system
- The molecule
Niels Bohr's 1913 model pictured electrons orbiting the nucleus in fixed energy levels, jumping between them by absorbing or emitting quanta of energy. This explained the spectral lines of hydrogen with remarkable accuracy. Bohr won the Nobel Prize in Physics in 1922 for this work.
2. What is the positively charged particle found in the nucleus of an atom?
- Neutron
- Electron
- Proton
- Photon
Protons carry a positive electric charge and, together with neutrons, make up the atomic nucleus. The number of protons in an atom's nucleus defines which chemical element it is. Ernest Rutherford is credited with identifying and naming the proton in the early 1920s.
3. Which scientist proposed that light and matter can behave as both particles and waves, a concept known as wave-particle duality for matter?
- Louis de Broglie
- Isaac Newton
- Michael Faraday
- James Clerk Maxwell
In his 1924 doctoral thesis, Louis de Broglie proposed that particles such as electrons have an associated wavelength, extending wave-particle duality from light to matter. His idea was soon confirmed by experiments showing electron diffraction. De Broglie received the Nobel Prize in Physics in 1929.
4. Albert Einstein won the 1921 Nobel Prize in Physics primarily for explaining which quantum phenomenon?
- Gravitational lensing
- General relativity
- The photoelectric effect
- Brownian motion
Einstein explained the photoelectric effect in 1905 by proposing that light comes in discrete packets of energy called quanta, later named photons. Notably, he did not win the Nobel Prize for his famous theories of relativity. This work helped lay the foundation for quantum mechanics.
5. Werner Heisenberg is famous for a principle stating that you cannot simultaneously know both the exact position and exact momentum of a particle. What is it called?
- The equivalence principle
- The uncertainty principle
- The correspondence principle
- The exclusion principle
Formulated in 1927, Heisenberg's uncertainty principle sets a fundamental limit on how precisely certain pairs of properties, like position and momentum, can be known at once. It is not a limitation of measuring instruments but a basic feature of nature. Heisenberg won the Nobel Prize in Physics in 1932.
6. What is the negatively charged particle that orbits the nucleus of an atom?
- Positron
- Neutron
- Electron
- Proton
The electron was the first subatomic particle discovered, identified by J.J. Thomson in 1897. It carries a negative electric charge and is roughly 1,800 times lighter than a proton. Electrons are responsible for chemical bonding and the flow of electric current.
7. Which physicist directed the famous gold foil experiment that revealed the atom has a small, dense, positively charged nucleus?
- John Dalton
- Ernest Rutherford
- J.J. Thomson
- Max Planck
In the 1909 gold foil experiment, alpha particles fired at thin gold foil occasionally bounced almost straight back, which Rutherford said was as astonishing as a shell bouncing off tissue paper. This showed atoms are mostly empty space with a tiny, dense nucleus. Rutherford is often called the father of nuclear physics.
8. Max Planck is regarded as the originator of quantum theory. In what year did he introduce his quantum hypothesis to explain black-body radiation?
- 1925
- 1875
- 1945
- 1900
In 1900 Max Planck proposed that energy is emitted or absorbed in discrete units called quanta, solving the black-body radiation problem. He introduced a fundamental constant, now called Planck's constant, central to all of quantum physics. Planck won the Nobel Prize in Physics in 1918.
9. What term describes atoms of the same element that have different numbers of neutrons?
- Allotropes
- Isomers
- Isotopes
- Ions
Isotopes share the same number of protons but differ in their neutron count, giving them different atomic masses. Carbon-12 and carbon-14 are isotopes of carbon, with carbon-14 used in radiocarbon dating. The word isotope was suggested by Margaret Todd to Frederick Soddy in 1913.
10. Wolfgang Pauli's exclusion principle states that no two electrons in an atom can have the same set of what?
- Electric charges
- Quantum numbers
- Orbital shapes
- Masses
Pauli's exclusion principle, stated in 1925, forbids two electrons in an atom from occupying the same quantum state, meaning they cannot share all four quantum numbers. This principle explains the structure of the periodic table and why matter takes up space. Pauli won the Nobel Prize in Physics in 1945.
11. Marie Curie was a pioneer in the study of radioactivity and won Nobel Prizes in two different sciences. Which two?
- Chemistry and Medicine
- Physics and Chemistry
- Chemistry and Biology
- Physics and Medicine
Marie Curie won the Nobel Prize in Physics in 1903 for research on radioactivity and the Nobel Prize in Chemistry in 1911 for discovering the elements polonium and radium. She remains the only person to win Nobel Prizes in two different sciences. The element curium is named in honor of her and her husband Pierre.
12. In quantum mechanics, what is the name of the equation, formulated in 1926, that describes how the quantum state of a system changes over time?
- The Dirac equation
- The Boltzmann equation
- The Schrödinger equation
- The Maxwell equation
Erwin Schrödinger's wave equation, published in 1926, describes the behavior of quantum systems using a wave function. It became one of the central pillars of quantum mechanics. Schrödinger shared the 1933 Nobel Prize in Physics with Paul Dirac.
13. Bohr and Einstein famously debated the interpretation of quantum mechanics. Which interpretation, associated with Bohr's institute, became the standard early view?
- The pilot-wave interpretation
- The Copenhagen interpretation
- The ensemble interpretation
- The many-worlds interpretation
The Copenhagen interpretation, developed largely by Bohr and Heisenberg in the 1920s, holds that a quantum system exists in a superposition of states until it is measured. It is named after the city where Bohr's institute was located. Einstein resisted this view, famously insisting that God does not play dice.
14. The neutron, the electrically neutral particle in the nucleus, was discovered in 1932 by which British physicist?
- Paul Dirac
- Arthur Eddington
- James Chadwick
- William Crookes
James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles and detecting a neutral, penetrating radiation. The neutron's discovery completed the basic picture of the atomic nucleus. Chadwick was awarded the Nobel Prize in Physics in 1935.
15. Paul Dirac's 1928 equation combined quantum mechanics with special relativity and predicted the existence of what?
- Antimatter
- Dark matter
- The neutrino
- The Higgs boson
The Dirac equation predicted the existence of the positron, an antimatter counterpart of the electron, which Carl Anderson observed experimentally in 1932. This launched the study of antimatter, where each particle has an oppositely charged partner. Dirac shared the 1933 Nobel Prize in Physics with Erwin Schrödinger.