4.4 PHYSICAL SCIENCE
WHAT I CAN DO
11 HUMSS B OUR LADY OF SORROWS
:KAZELEEN JOY G. SUPNET
:Experimental evidence that electrons can behave like waves
:Scientists behind the experiments
Electrons Act
Like Waves
DAVISSON AND GERMER
Showed in 1927 that electrons scatter from a crystal
the way x-rays do, proving that particles of matter
can act like waves. A broken apparatus
serendipitously lead to the discovery.
A 1927 paper in the Physical Review demonstrated that particles of matter can act like waves,
just as light waves sometimes behave like particles. Clinton Davisson and Lester Germer of the Bell
Telephone Laboratories, then in New York, found that electrons scatter from a crystal in the same
way that x rays do. Davisson won the Nobel Prize for his thesis, which started as a result of a
laboratory accident.
Louis de Broglie, a graduate student at Paris University at the time, suggested that matter, like
light, has a dual existence in 1924. The following year, graduate student Walter Elsasser of the
University of Göttingen in Germany suggested a method to test it: since electrons have a wave
nature, they can show wave effects such as diffraction, much like light.
A light beam going through a typical sequence of holes or slits, such as a grating, experiences
“dark spots” in directions where the wave troughs from certain holes cancel the peaks from others.
“Bright spots” emerge as the peaks reinforce one another. A beam of tiny marbles, as electrons were
previously conceived, could never exhibit such cancellation and enhancement.
It wasn't until Davisson shared his findings with physicists during a summer holiday in England
in 1926 that he heard about de Broglie's theory and discovered that his data undoubtedly contained
the world's first glimpse of electron diffraction. The recrystallized nickel's atoms had served like a
grating.
Following this realization, Davisson and Germer embarked on a systematic quest for diffraction
patterns, especially peaks in their data plots that would imply extra electrons scattering in specific
directions. After some initially surprising findings, they discovered a single plateau that agreed with
both de Broglie's hypothesis and independent observations using x rays instead of electrons.
 They eventually discovered 30 peaks, 29 of which were explained by
diffraction. One remained unidentified, and they were unable to locate eight
additional peaks that they had expected to see.
 According to Spencer Weart, director of the Center for History of Physics at
the American Institute of Physics in College Park, Maryland, Davisson and
Germer are often misrepresented as “experimentalists attempting to confirm
a theoretical prediction.” In reality, after they heard about de Broglie's idea,
they merely repurposed an experimental program that had already been
running for another reason,
 “This is one of the occasions where experimenters obtained evidence that
they later discovered was important to a hypothesis that they had never set
out to test.” - Weart
Here are some pictures I can show you about the
experiment of the two said scientists
CLINTON DAVISSON
 discovered electron diffraction, for which he was awarded the 1937 Nobel Prize in Physics.
 Lived 1881 – 1958
 His discovery confirmed the de Broglie hypothesis that particles can behave as waves.
 A brilliant and careful scientist, financial difficulties interrupted his undergraduate studies; it
took him six years to get a B.S. in physics.
 During World War I, he worked on war projects at Bell Laboratories. His fundamental
knowledge proved so valuable that the company created a special pure research
position for him when the war ended.
LESTER HALBERT GERMER
 born Oct. 10, 1896, Chicago, Ill., U.S. American physicist who, with his colleague Clinton
Joseph Davisson, conducted an experiment (1927) that first demonstrated the wave
properties of the electron.
 This experiment confirmed the hypothesis of Louis-Victor de Broglie, a founder of wave
mechanics, that the electron should show the properties of an electromagnetic wave as
well as those of a particle.
 died Oct. 3, 1971, Gardiner, N.Y.
 Germer was a graduate student at Columbia University, working under Davisson’s
supervision at the Bell Telephone Laboratories in New York City,
 He was awarded the Elliott Cresson Medal in 1931.
 A former fighter pilot in World War I, Germer subsequently worked at Bell Labs in New
Jersey.