Robert Millikan
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Born March 22,1868 in
Morrison, Ill.
Died on December 19,1953in
San Marino, California.
Attended Oberlin College in
Ohio. (1886-1891)
Obtained master degree in
physics at Colombia
University in 1893.
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Worked as a physics teacher.
Professor at the University of Chicago for 11
years.
He discovered accurate charge of an electron
using “Falling drop method.”
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Verified Einstein's photoelectric equation.
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Won the Nobel Prize for physics in 1923.
Experimental Design
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The oil is sprayed into the chamber above the two parallel
charged plates.
The oil drops through a hole in the top plate.
X rays cause the air particles to lose electrons which then
stick to the oil droplets. This causes the oil droplets to have
a negative charge.
Millikan could control the rate of the droplets charge by
varying the intensity of the electric field. (Basically, he
could make the oil droplets float in mid-air using invisible X
rays.)
Postulates of Theory
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Millikan figured out that the magnitude of each drop's charge
increased slightly and he determined that the smallest
common denominator was 1.602 x10^-19 coulombs. (The
coulomb is the unit for electric charge.)
In order to make things easier, Millikan made 6.02 x10^-19
equal to 1-. From there, he based everything else off of that.
From knowing Thomson's charge-to-mass ratio, Millikan then
figured out the mass of an electron. (Look at page 109 in the
textbook for equation.)
Works Cited
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Buthelezi, Thandi, et al. Chemistry: Matter and Change. New
City:
McGraw Hill Glencoe, 2008.
York
The Nobel Foundation. "Robert A. Millikan Robert Millikan: The Nobel
Prize in Physics 1923."Nobel Prizes. The Nobel Foundation. 22 Oct.
2007 <http://nobleprize.org/nobelprizes/physics/laureates/1923/millikanbio.html>.
"Determination of the Charge on the Electron: Thomson and Robert
Millikan." Atomic Structure Table of Contents. ChemTeam. 23
Oct. 2007 <http://dbhs.wvusd.k12.ca.us