(2019-08-30) Röntgen's X-rays (1895).
An electromagnetic form of ionizing radiation, not so identified at first.
On 8 November 1895,
Wilhelm Röntgen (1845-1923)
was busy experimenting with a Crookes tube
(such cathode-ray tubes had been invented about twenty years earlier by
William Crookes, 1832-1919).
Röntgen saw that a nearby piece of
barium platinocyanide
Ba [Pt(CN)4 ]
gave off light when the tube was powered.
He figured that an unknown type of penetrating radiation
(which he thus dubbed X-rays) was created when the softer cathode rays
hit the glass walls of the tube, making the barium platinocyanide
fluoresce across the room.
At that time, the exact nature of cathode-rays was also unknown,
albeit more familiar. Cathode rays were only identified as
beams of electrons in 1895, by
Jean Perrin (1870-1942)
and in 1896 by
J.J. Thompson (1870-1942).
Against Röntgen original guess, X-rays are actually
a form of electromagnetic radiation (photons).
Rötgen spent seven straight weeks investigating the discovery
and showed how X-rays can penetrate paper, wood,
aluminum and soft human tissue to varying degrees.
Their effect on photographic plates allowed medical imagery,
which Röntgen first demonstrated with a famous photo
of the bones in the left hand of his wife,
Anna Bertha (1872-1919).
When she was showed the picture, she said
"I have seen my death" (1895-12-22).
(2019-08-31) X-ray crystallography (Max von Laue, 1912).
X-ray diffraction patterns reveal the structure of crystals.
Crystallography started in 1611 when
Kepler
cataloged the symmetries of ice crystals.
The field was revolutionized in 1912,
when Max von Laue (1879-1960) found
that X-rays are diffracted by crystals. The resulting diffraction patterns reveal
the periodic structure of the crystal.
For this, Max von Laue received the 1914 Nobel prize for physics.
His discovery was immediately followed by the work of the Braggs (father & son)
for which they shared the 1915 Nobel prize.
The first X-Ray spectrometers were made by
C.H. Jenkinson (18??-1939)
who had been recently put in charge of the physics workshop at the
University of Leeds.
Bragg's Law (1912)
n l = 2 d sin q
30 Nobel prizes
have been awarded for crystallography-related work.
(2019-11-23) Radiation Dose (1 mRem / day from natural background).
Radiation energy absorbed by human tissue (per unit of mass).
The international unit for radiation dose is the sievert (symbol Sv)
which correspond to 1 joule deposited by radiation in 1 kg of typical mammalian tissue.
1 Sv is a very large dose. In the US and elesewhere, the
Rem is still used which is 100 times less (this stands for
radiation equivalent mammalian, formerly
Röntgen Equivalent for Man). That's still too large a unit for everyday use,
for which the millirem (mRem) submutiple is most popular
(possibly because 1 mRem / day is roughly the dose corresponding
to typical natural sources at sea level, often quoted as 320 mRem/yr).
A late 1960's Homer Laughlin Fiesta Ironstone "mango red" bowl, 6.5" in diameter, 1.75" deep.
The 0.2 mm glaze owes its color to UO3, trioxide of depleted uranium
(0.25% of U-235) which is about 60% less radioactive than natural uranium.
Originally
(from 1936 to 1943)
the Homer Laughlin Company of West Virginia used natural uranium
(0.72% of U-235) for "Fiesta red".
