A centenary of the discovery of the nucleus: Ernest Rutherford
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A presentation given at the HNPS2011
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A centenary of the discovery of the nucleus: Ernest Rutherford
- 1. A centenary of the discovery of the nucleus Theo J. Mertzimekis Saturday, June 4, 2011
- 2. The life and works of Sir Ernest Rutherford ⚛ Some Bio ⚛ The Gold Foil experiment ⚛ The nucleus & the model of the atom ⚛ Milestones & Major Achievements Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 3. Some Bio ⚛ Born in Spring Grove, NZ on Aug 30, 1871 to James and Martha Rutherford ⚛ 2nd son, 4th child of total 12 children ⚛ Father: engineer; Mother: teacher ⚛ 1890: Canterbury College in Christchurch ⚛ Graduates with BA in 1892 (Pure Math, Latin, Physics) Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 4. College years ⚛ Due to his math skills he received a scholarship to continue his studies ⚛ MA degree: original work in EM / inspired by Tesla and his coil. He tries to determine if iron stays magnetized under high-‐frequency currents ⚛ For that purpose he constructed two separate devices, one to provide 10μs pulses and a magnetic detector Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 5. @ Cambridge ⚛ Conducts second degree in Geology and Chemistry to comply with a Royal Scholarship requirements ⚛ He gets the Scholarship and joins J.J. Thomson at Cambridge as the first non-‐Cambridge graduate to be accepted for research. ⚛ He improves his detector to measure frequencies and study the dielectric properties of insulators. Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 6. First Steps in Research ⚛ He constructs an EM detector and improves it to apply it to sea navigation (range ~ 200 m) ⚛ Thomson invites him to study the electrical conduction of gases. He uses high-‐f currents, X-‐ rays and radioactivity to initiate electrical conduction. ⚛ Radioactivity itself intrigued him and soon he tries to understand its nature. Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 7. @ McGill ⚛ w/ Brookes: Discovery of Radon (inert, radioactive gas) ⚛ w/ Soddy: Discovery of radioactive decay law. Some heavy atoms decay to lighter species. This works attracts the world’s attention ⚛ Fellow of the Royal Society of Canada (1900) and London (1903). He publishes “Radio-‐activity” in 1904 and “Radioactive transformations” in 1906 Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 8. The Nobel Prize ⚛ 1908 -‐ Chemistry "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances". Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 9. @ Manchester ⚛ Schuster steps down and Rutherford becomes a Professor at Manchester ⚛ w/ Geiger: Show that α particles are He atoms stripped of their electrons. ⚛ w/ Geiger: Develop the Rutherford-‐Geiger detector to count single atoms produced in radioactive decays ⚛ focus on measuring physical constants, e.g. Avogadro’s number Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 10. Geiger & Marsden ⚛ They were instructed to study reflection of α particles impinging metals ⚛ In 1909, G&M reported that some α particles kept bouncing back, even from a thin sheet of Au “It is as if someone had fired a 15” naval shell at a piece of tissue and that bounced straight on us” 10.1098/rspa.1909.0054 Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 11. The experiment Zinc Sulfide Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 12. Rutherford’s atom model ⚛ Classical picture / Planetary configuration ⚛ Main problems: ⚛ electrons should lose energy (spiral orbits) ⚛ continuous e-‐ spectra were not observed Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 13. Rutherford & Bohr ⚛ Niels Bohr came to work with Rutherford ⚛ In 1915, Bohr used the planetary model but placed the electrons in specific orbits applying the principles of Quantum Mechanics Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 14. Rutherford scattering ⚛ Rutherford calculated the cross section of the scattering using classical physics 2 2 1 Z1 Z2 e 1 σR (θ) = 4 2E sin4 (θ/2) doi: 10.1080/14786440508637080 Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 15. Major achievements ⚛ Discovered the concept of half-‐life ⚛ Discovered radioactive transmutation via the reaction α + 14N → 17O + p ⚛ Differentiated α,β radiation (Nobel) ⚛ Postulated the existence of the nucleus ⚛ Postulated the existence of the neutron Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 16. Splitting the atom ⚛ Though not in a controlled way, Rutherford was the first to split the atom ⚛ John Cockroft and Ernest Walton finally did it in a controlled way in 1932 using their high-‐voltage electrostatic accelerator. ⚛ w/ Oliphant built a lower-‐V with improved flux and used it to bombard 2D on 2D, thus ending up in discovering 3H and 3He Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 17. Other work ⚛ During WW1, he worked on hydrophones. He suggested the use of circus sea lions to detect enemy submarines ⚛ Dated the age of Earth ⚛ Developed the Rutherford-‐Geiger detector ⚛ Invented the first smoke detector Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 18. Honors Awards ⚛ 1914 / Knighted ⚛ 1925 / Order of Merit ⚛ 1931 / Peerage ⚛ 1997/ Rutherfordium (Z=104) ⚛ Several other medals (Franklin, Mateucci, Copley, Elliot Cresson, Rumford) Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 19. The legend his legacy ⚛ Died in 1937 due to implications of a delayed operation ⚛ His ashes are buried next to Sir Isaac Newton ⚛ Rutherford is the Father of Nuclear Physics ⚛ He is to Nuclear Physics what Darwin is to Evolution, Einstein to Relativity, Newton to Mechanics Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 20. “The Crocodile” Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011
- 21. Outro... In Science there is only Physics; all the rest is stamp collecting Theo J. Mertzimekis UoAthens / HNPS2011 Saturday, June 4, 2011