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Early Experiments in Quantum Physics 225

DE BROGLIE MATTER WAVES

We now come to a mysterious concept first put forth by Prince Louis De Broglie in 1923.
Roughly, here is the reasoning due to De Broglie.

2
c ¼ ln, Hertz 1888, E ¼ hn, Planck 1901, E ¼ mc , Einstein 1905 [9]

hc h h
2
E ¼ hn ¼ ¼ mc ) l light ¼ ) l matter? ¼ , De Broglie 1923 [6]
l mc mv
light matter?
The problem with interpretation of this idea of ‘‘matter waves’’ is that waves should exhibit
diffraction which is not commonly observed macroscopically. Consider a typical rifle bullet of
4.2 g traveling at a speed of 965 m=sec. The De Broglie matter wavelength for that bullet would be
2
h 6:62609 10 34 J s 34 kg(m=s) s 34
ffi 1:635 10 ¼ 1:635 10 m which is smal-
l ¼ ¼
mv (0:0042 kg)(965 m=s) kg m=s
ler than any available technique can measure! On the other hand, consider the De Broglie
wavelength of an electron with 5 eV of energy as a typical circumstance within a molecule
(Figure 10.11).

FIGURE 10.11 Louis-Victor Pierre Raymond De Broglie (1892–1987) was a French scientist who wrote a
revolutionary PhD thesis in 1924 that formed the basis for Schrödinger’s wave mechanics in 1926. De Broglie
was awarded the Nobel Prize in physics in 1929. He also received the Henri Poincare Medal in 1929 and the
Albert I of Monaco prize in 1932. De Broglie had been an officer in the French Army during World War I
stationed at radio facilities at the Eiffel Tower and had read about radio waves and some of Einstein’s relativity
papers. After the war, he enrolled in a doctoral program at the University of Paris and wrote a revolutionary
paper in 1923 [6], which was the basis for his PhD thesis in 1924. However, none of his professors understood
the idea, and his thesis was rejected until the Chair of the Department of Physics, Prof. Pierre Langevin, sent the
thesis to Einstein who approved it and De Broglie was awarded the PhD for his work. Actually, the work was
based on Einstein’s special relativity and we remind the reader that what is often called ‘‘nonrelativistic wave
mechanics’’ is already based on a relativistic principle.