C.T.R. Wilson
Charles Wilson is 2nd from right in the front row.Can you find Paul Langevin and O.W. Richardson?
Nobel Prizewith Compton
1927
2 major paperswith illustrationspublished 1923
first photos ofα,β particles
1911
first chamber- x ray photos
1895
Cloud Chamber
" published Theory of "Thundercloud Electricity
1956
promoted to Reader of Electrical Meteorology
1918
. Observer in Met Physics Solar Physics Observatory
1913appointed
Meteorological Societyemployment
1899
AtmosphericElectricity
MAJOR INTERESTS
“the most original and wonderful instrument in scientific history.”
- Rutherford
• ALPHA broad, straight track
• BETA thin, bending track
• GAMMA no tracks as too few ions are
produced in the air
1911 photo
1912 Wilson photo
Compton Scattering : What?
• X-ray photons collide with electrons in carbon atoms.
• The scattered photons are shifted to longer wavelengths (lower energies).
incoming
photon λiscattered
photonλse- at reste-
recoil
angleθ
Compton Scattering : So What?
• The particle theory of light was still controversial in the 1920’s, despite Einstein’s photoelectric effect.
• Compton used a particle model of the photon, and classical conservation of momentum, to explain the shift in wavelength of the observed scattered x-rays.
Δλ = hmec(1-cosθ)
• evidence of Compton Effect (Nobel Prize Compton & Wilson 1927)
• evidence of transmutation of elements (Rutherford’s N + α -> O + p)
• discovery of positron and the pair creation-annihilation of electrons & positrons (Nobel Prize Anderson 1936)
• discovery of muon
• P. BLACKETT “counter controlled cloud chamber” (Nobel Prize 1948) added a Geiger Counter above & below the c.c. Cosmic rays triggered gas expansion and their own photos when impulses hit both counters simultaneously.
• D.A. GLASER “bubble chamber” replaced the c.c. in 1952, using liquid He or H2. Higher density medium allowed photos of high-E particles that were too fast for the c.c.
Beyond the Cloud Chamber
Web Resources
• http://home.houston.rr.com/molerat/cloud.htm how to make a cloud chamber
• http://www.nobel.se/physics/laureates/1948/press.html Wilson’s Nobel address
• http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/comptint.html#c1 Compton Effect
• http://www.boltlightningprotection.com/lightning_physics.htm lightning physics
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