Microbiology and Immunology

Broglie, Louis Victor de WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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award in recognition of his development of the biotechnology

sector in British Columbia.

See alsoMicrobial genetics

BBroglie, Louis Victor deROGLIE, LOUISVICTOR DE(1892-1987)

French physicist

Louis Victor de Broglie, a theoretical physicist and member of

the French nobility, is best known as the father of wave

mechanics, a far-reaching achievement that significantly

changed modern physics. Wave mechanics describes the

behavior of matter, including subatomic particles such as elec-

trons, with respect to their wave characteristics. For this

groundbreaking work, de Broglie was awarded the 1929

Nobel Prize for physics. De Broglie’s work contributed to the

fledgling science of microbiology in the mid-1920s, when he

suggested that electrons, as well as other particles, should

exhibit wave-like properties similar to light. Experiments on

electron beams a few years later confirmed de Broglie’s

hypothesis. Of importance to microscopedesign was the fact

that the wavelength of electrons is typically much smaller than

the wavelength of light. Therefore, the limitation imposed on

the light microscope of 0.4 micrometers could be significantly

reduced by using a beam of electrons to illuminate the speci-

men. This fact was exploited in the 1930s in the development

of the electron microscope.

Louis Victor Pierre Raymond de Broglie was born on

August 15, 1892, in Dieppe, France, to Duc Victor and Pauline

d’Armaille Broglie. His father’s family was of noble

Piedmontese origin and had served French monarchs for cen-

turies, for which it was awarded the hereditary title Duc from

King Louis XIV in 1740, a title that could be held only by the

head of the family.

The youngest of five children, de Broglie inherited a

familial distinction for formidable scholarship. His early edu-

cation was obtained at home, as befitted a great French family

of the time. After the death of his father when de Broglie was

fourteen, his eldest brother Maurice arranged for him to obtain

his secondary education at the Lycée Janson de Sailly in Paris.

After graduating from the Sorbonne in 1909 with bac-

calaureates in philosophy and mathematics, de Broglie entered

the University of Paris. He studied ancient history, paleogra-

phy, and law before finding his niche in science, influenced by

the writings of French theoretical physicist Jules Henri

Poincaré. The work of his brother Maurice, who was then

engaged in important, independent experimental research in x

rays and radioactivity, also helped to spark de Broglie’s inter-

est in theoretical physics, particularly in basic atomic theory.

In 1913, he obtained his Licencié ès Sciences from the

University of Paris’s Faculté des Sciences.

De Broglie’s studies were interrupted by the outbreak of

World War I, during which he served in the French army. Yet,

even the war did not take the young scientist away from the

country where he would spend his entire life; for its duration,

de Broglie served with the French Engineers at the wireless

station under the Eiffel Tower. In 1919, de Broglie returned to

his scientific studies at his brother’s laboratory. Here he began

his investigations into the nature of matter, inspired by a

conundrum that had long been troubling the scientific com-

munity: the apparent physical irreconcilability of the experi-

mentally proven dual nature of light. Radiant energy or light

had been demonstrated to exhibit properties associated with

particles as well as their well-documented wave-like charac-

teristics. De Broglie was inspired to consider whether matter

might not also exhibit dual properties. In his brother’s labora-

tory, where the study of very high frequency radiation using

spectroscopes was underway, de Broglie was able to bring the

problem into sharper focus. In 1924, de Broglie, with over two

dozen research papers on electrons, atomic structure, and x

rays already to his credit, presented his conclusions in his doc-

toral thesis at the Sorbonne. Entitled “Investigations into the

Quantum Theory,” it consolidated three shorter papers he had

published the previous year.

In his thesis, de Broglie postulated that all matter—

including electrons, the negatively charged particles that orbit

an atom’s nucleus—behaves as both a particle and a wave.

Wave characteristics, however, are detectable only at the

atomic level, whereas the classical, ballistic properties of mat-

ter are apparent at larger scales. Therefore, rather than the

wave and particle characteristics of light and matter being at

odds with one another, de Broglie postulated that they were

essentially the same behavior observed from different per-

spectives. Wave mechanics could then explain the behavior of

all matter, even at the atomic scale, whereas classical

Newtonian mechanics, which continued to accurately account

for the behavior of observable matter, merely described a spe-

cial, general case. Although, according to de Broglie, all

objects have “matter waves,” these waves are so small in rela-

tion to large objects that their effects are not observable and no

departure from classical physics is detected. At the atomic

level, however, matter waves are relatively larger and their

effects become more obvious. De Broglie devised a mathe-

matical formula, the matter wave relation, to summarize his

findings.

American physicist Albert Einstein appreciated the sig-

nificant of de Broglie’s theory; de Broglie sent Einstein a

copy of his thesis on the advice of his professors at the

Sorbonne, who believed themselves not fully qualified to

judge it. Einstein immediately pronounced that de Broglie

had illuminated one of the secrets of the Universe. Austrian

physicist Erwin Schrödinger also grasped the implications of

de Broglie’s work and used it to develop his own theory of

wave mechanics, which has since become the foundation of

modern physics.

De Broglie’s wave matter theory remained unproven

until two separate experiments conclusively demonstrated the

wave properties of electrons—their ability to diffract or bend,

for example. American physicists Clinton Davisson and Lester

Germer and English physicist George Paget Thomson all

proved that de Broglie had been correct. Later experiments

would demonstrate that de Broglie’s theory also explained the

behavior of protons, atoms, and even molecules. These prop-

erties later found practical applications in the development of

magnetic lenses, the basis for the electron microscope.

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