The Nobel prize centenary in physics
The report is dedicated to the discovery of X-rays and their revolutionary effect on the formation and development of modern physics.
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| Veröffentlicht in: | Вопросы атомной науки и техники |
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| Datum: | 2001 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2001
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| Zitieren: | The Nobel prize centenary in physics / A.N. Dovbnya, V.A. Shendrik, A.A. Shendrik // Вопросы атомной науки и техники. — 2001. — № 3. — С. 33-34. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859655794665979904 |
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| author | Dovbnya, A.N. Shendrik, V.A. Shendrik, A.A. |
| author_facet | Dovbnya, A.N. Shendrik, V.A. Shendrik, A.A. |
| citation_txt | The Nobel prize centenary in physics / A.N. Dovbnya, V.A. Shendrik, A.A. Shendrik // Вопросы атомной науки и техники. — 2001. — № 3. — С. 33-34. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The report is dedicated to the discovery of X-rays and their revolutionary effect on the formation and development of modern physics.
|
| first_indexed | 2025-12-07T13:39:18Z |
| format | Article |
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THE NOBEL PRIZE CENTENARY IN PHYSICS
A.N. Dovbnya, V.A. Shendrik, A.A. Shendrik1
Scientific-Production Complex “Accelerator”
National Science Center “Kharkov Institute of Physics and Technology”
1, Akademicheskaya St., 61108 Kharkov, Ukraine
1 Secondary School, Valki, Kharkov Region, Ukraine
The report is dedicated to the discovery of X-rays and their revolutionary effect on the formation and development
of modern physics.
PACS numbers: 01.90.+g, 01.65.+g
On the 10th of 1901, in the Large Hall of the Acade-
my of Music in Stockholm the Nobel Prize Committee
awarded Roentgen with the first Nobel Prize in physics
as a mark of gratitude of scientists and the mankind.
Wilhelm Konrad Roentgen was born in a small Ger-
man town of Lennepe not far off from the Germany-
Netherlands frontier. He devoted all his life to physics.
Having become Professor of Physics, Roentgen gave
lectures on physics at a number of institutes in Ger-
many.
The physical experiment was in his element. Hardly
anybody could be compared with him in thinking out
the experiment, in the accuracy of measurements and in
thoroughness of analyzing possible mistakes. Roentgen
had already become famous among physicists of that
time for his investigations in various areas. Thus, for
example, in 1890, he was the first to prove by direct
experiment that moving charges generate a magnetic
field. At the end of the 19th century, W. Roentgen,
Professor of the Wurzburg University in Germany,
conducted experiments with electric discharge in gases.
He used a glass tube having two electrodes soldered in
it and pumped down to a pressure of about 10-5 of at-
mospheric pressure. When a high voltage was applied
to the electrodes, the glass about the anode started
glowing with a yellow-green light. This glow was at-
tributed by physicists to the action of the so-called
cathode rays, the flux of which was emitted by the
cathode, and was incident on the anode and, partially,
on the tube walls.
One November evening of 1895, when working in
the laboratory, Roentgen hit upon an unusual phe-
nomenon. For experiments, he wrapped the discharged
tube with a black light-proof paper. It was dark in the
room, and this allowed the scientist to notice that the
barium salt crystals lying not far from the tube radiated
a faint light. He deenergized the tube and the lumines-
cence disappeared. Then Roentgen placed a barium salt-
coated screen not far from the tube, and the screen start-
ed glowing. The scientist began placing different objects
between the tube and the screen. Cardboard, paper,
ebonite plates exerted no effect on the brightness of the
glow. Metal subjects cast a shadow on the screen. Evi-
dently, the tube was a source of unknown penetrating
rays, X rays, as Roentgen called them, or Roentgen rays
as we now call them.
The researcher put his hand in the path of X-rays,
and a dark image of the hand skeleton appeared on the
screen - soft tissues were transparent to the radiation,
while the bones were nearly opaque to it.
A unique talent of physicist-experimenter, excep-
tional powers of observation, and a firm rule to attain
clarity in everything permitted Roentgen to discover the
phenomenon which had been for many years close by
the scientists who made experiments using the same de-
vices.
However, the character of this new radiation re-
mained enigmatic. Only one thing was clear, i.e., the ra-
diation could not be identified with the cathode rays.
Similarly to the cathode rays, it gave rise to fluores-
cence, had a chemical action, propagated in straight
lines, formed shadows. However, the X-rays did not
have the characteristic properties of the cathode rays -
they were not deflected by the magnetic field. Maybe
they were of the same nature as the ultraviolet radiation
was? But in that case they should be appreciably reflect-
ed, refracted, polarized.
Those were the questions (repeating an attempt to
explain the nature of the rays), with which Roentgen
finished his first work on X-rays, reported at the Physics
Institute of the Wurzburg University in December,
1895.
The first article of the scientist “About a new kind of
rays”, where he described the properties of the radiation
discovered by him, aroused an enormous interest
throughout the world and was then published as a sepa-
rate brochure in all European languages.
The second work reported on 5 March, 1896, com-
prised two new essential facts. The first was that under
the action of X-rays the electrified bodies get dis-
charged. It is not the X-rays themselves but the air pene-
trated by them that acquires the property to discharge
the electrified bodies. The second important fact men-
tioned even in the first Roentgen′s work was that X-rays
were produced with the cathode rays hitting not only the
glass of discharge tubes, but also any substance, not ex-
cluding liquids and gases. Depending on the character
of substance struck by the cathode rays, the intensity of
the resulting X-radiation turned out to be different.
Those observations brought Roentgen as early as in
February, 1896, to the development of the “focus” tube,
where a concave aluminum mirror served as a cathode
and a platinum plate placed at the centre of curvature of
the mirror and inclined at 45° to the mirror axis served
as an anode. Before the advent of thermionic devices,
the “focus tubes were the only setups to produce X-rays
for medical and physical investigations. Roentgen did
much to quickly promote his discovery, having rejected
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №3.
Серия: Ядерно-физические исследования (38), с. 33-34.
33
with his characteristic disinterestedness any possibility
of making a profit from it. The general interest much
contributed to a rapid progress of X-ray engineering. It
will suffice to give only one example to illustrate the
path covered: in 1896 the radiography of a hand took a
20 min exposure, while now an instant is sufficient for
the purpose.
The physicists who held the viewpoint that X-rays
were the electromagnetic radiation naturally tried to de-
tect not the reflection but the diffraction on extremely
narrow slits, as dictated by the supposed small value of
X-ray wavelength. However, the man-made slits, no
matter how narrow they were, appeared to be too rough.
Besides, it was clear that it was difficult, if possible, to
find the mechanical way of scribing rulings being well
off at a distance of about a molecular size. In 1912, the
German physicist M. Laue put forward a bold idea to
use crystals as diffraction gratings for X-rays. In the
same year, the theory was corroborated by experiments.
In 1914, for the discovery of X-ray diffraction by crys-
tals M. Laue was awarded the Nobel Prize in physics.
And yet, Roentgen could not explain the nature of
enigmatic rays. He did not know about the existence of
electrons, and it was their slowing down in the tube
glass that was the reason for the appearance of X-rays
and a greenish visible light. When a charged particle
comes flying into the substance, it slows down, loses its
velocity and emits electromagnetic waves. The X-radia-
tion wavelengths range from 5⋅10-8 to 5⋅10-12 m. On the
scale of electromagnetic waves they take the place be-
tween ultraviolet radiation and gamma-radiation. The
beam of slowing down electrons emits waves of a wide
diversity of wavelengths. These waves form a continu-
ous X-ray spectrum. The wavelength which accounts for
the maximum intensity of radiation should decrease as
the electron velocity increases, i.e., as the tube voltage
increases. Experiments have established the short wave-
length boundary of the continuous X-ray spectrum λmin =
12390/U, where λmin is expressed in angstroms, and U -
in volts.
The existence of the short wavelength boundary di-
rectly follows from the quantum nature of the radiation.
Really, if the radiation arises at the expense of energy
lost by the electron in its slowing down, then the quan-
tum value ħω cannot exceed the electron energy eU: ħ
ω ≤ eU. Hence it turns out that the radiation frequency
cannot exceed ωmax = eU/ħ, and therefore, the wave-
length cannot be smaller than λmin = 2πc/ωmax = = 2π
ħc/eU. Thus we have arrived at the empirical relation
given above. The ħ value found from these relations for
the Planck constant is in good agreement with the val-
ues calculated in other ways. Of all the methods of de-
termining ħ the method based on the measurement of
the sort wavelength boundary of the continuous X-ray
spectrum is believed to be most exact.
At a rather high electron velocity, apart from the
continuous X-ray radiation (i.e., the radiation due to
electron deceleration), the characteristic radiation is also
excited (generated by excitation of inner electron shells
of anticathode atoms). While the continuous X-radiation
is independent of the anticathode material and is deter-
mined only by the energy of electrons bombarding the
anticathode, the characteristic radiation is specified by
the nature of substance, from which the anticathode is
made. As long as the electron energy is insufficient to
excite the characteristic radiation, only continuous X-
ray radiation arises. At a sufficiently high energy of
bombarding electrons, sharp lines of the characteristic
spectrum appear against the background of the continu-
ous X-ray spectrum, the intensity of these lines being
many times higher than that of the background.
The characteristic X-rays were discovered in 1906
by the English physicist Ch. Barkla, and in 1917 he was
also awarded with the Nobel prize in physics. In 1913,
another English physicist H. Moseley established a sim-
ple law relating the frequency of spectral lines from the
characteristic X-ray radiation to the ordinal number of
the emitting element (Moseley law). The dependence
established by Moseley allows one to determine exactly
the atomic number of the given element from the mea-
sured wavelength of X-ray lines; it has played a great
role in the arrangement of elements in the periodic sys-
tem.
W. Roentgen devoted his life to classical physics.
But it was his discovery of “a new type of rays” that
was the starting point for the development of new
physics - physics of atom and atomic nucleus. In less
than half a year after the discovery of X-rays, in an at-
tempt to puzzle out their nature the radioactivity was
discovered, and a year later the electron was found with
their use.
The discovery of X-rays had extremely important
consequences for both scientific investigations and prac-
tical applications in medicine and industry. It will not be
an exaggeration to say that from this discovery new
present-day physics begins.
34
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| id | nasplib_isofts_kiev_ua-123456789-79225 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T13:39:18Z |
| publishDate | 2001 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Dovbnya, A.N. Shendrik, V.A. Shendrik, A.A. 2015-03-30T06:36:05Z 2015-03-30T06:36:05Z 2001 The Nobel prize centenary in physics / A.N. Dovbnya, V.A. Shendrik, A.A. Shendrik // Вопросы атомной науки и техники. — 2001. — № 3. — С. 33-34. — англ. 1562-6016 PACS nambers: 01.90.+g, 01.65. +g https://nasplib.isofts.kiev.ua/handle/123456789/79225 The report is dedicated to the discovery of X-rays and their revolutionary effect on the formation and development of modern physics. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники The Nobel prize centenary in physics До сторіччя присудження першої Нобелівської премії з фізики Article published earlier |
| spellingShingle | The Nobel prize centenary in physics Dovbnya, A.N. Shendrik, V.A. Shendrik, A.A. |
| title | The Nobel prize centenary in physics |
| title_alt | До сторіччя присудження першої Нобелівської премії з фізики |
| title_full | The Nobel prize centenary in physics |
| title_fullStr | The Nobel prize centenary in physics |
| title_full_unstemmed | The Nobel prize centenary in physics |
| title_short | The Nobel prize centenary in physics |
| title_sort | nobel prize centenary in physics |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79225 |
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