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هل تولد الحياة من رحم الموت؟؟؟ دراسة بحثية
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مراقب عام سابقا
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: 4
تاريخ الإنضمام :
Sep 2009
رقم العضوية :
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العالم جى جى طومسون ..مكتشف الالكترون يتيم الاب في سن السابعة عشرة.
أول من اكتشف الإليكترون هو جى جى تومسون حيث استخدم أشعة ضوئية سالبة الشحنة (كان قد اختبرها عند امرارها من خلال شحنة كهربية موجبة و سالبة كما فى البطارية فتنافرت مع السالبة) و مررها على بعض الذرات و أعاد التجربة عدة مرات فوجدها تتنافر فعرف أن شحنتها سالبة و أسماها الإليكترون.
Sir Joseph John "J. J." Thomson
,
OM
,
FRS
[1]
(18 December 1856 – 30 August 1940) was a
British
physicist
. In 1897, Thomson showed that
cathode rays
were composed of a previously unknown negatively charged particle, and thus is credited with the discovery and identification of the
electron
. Thomson is also credited with finding the first evidence for
isotopes
of a stable (non-radioactive) element in 1913 as part of his exploration into the composition of
canal rays
(positive ions) and with the invention of the
mass spectrometer
. Thomson was awarded the 1906
Nobel Prize in Physics
for the discovery of the electron and for his work on the conduction of
electricity
in gases.
Biography]
J. J. Thomson, 1861.
Joseph John Thomson was born in 1856 in
Cheetham Hill
,
Manchester
,
England
. His mother, Emma Swindells, came from a local textile family. His father, Joseph James Thomson, ran an antiquarian bookshop founded by a great-grandfather. He had a brother two years younger than him, Frederick Vernon Thoms
[2]
His early education was in small private schools where he demonstrated great talent and interest in science. In 1870 he was admitted to
Owens College
at the unusually young age of 14. His parents planned to enroll him as an apprentice engineer to
Sharp-Stewart & Co
, a locomotive manufacturer, but these plans were
cut short when his father died in 1873
He moved on to
Trinity College, Cambridge
in 1876. In 1880, he obtained his BA in mathematics (
Second Wrangler
and 2nd
Smith's Prize
) and MA (with
Adams Prize
) in 1883.
[3]
In 1884 he became
Cavendish Professor of Physics
. One of his students was
Ernest Rutherford
, who later succeeded him in the post. In 1890 he married Rose Elisabeth Paget, daughter of
Sir George Edward Paget
, KCB, a physician and then
Regius Professor of Physic at Cambridge
. He had one son,
George Paget Thomson
, and one daughter,
Joan Paget Thomson
, with her. One of Thomson's greatest contributions to modern science was in his role as a highly gifted teacher: seven of his research assistants and his son won Nobel Prizes in physics. His son won the Nobel Prize in 1937 for proving the wavelike properties of electrons.
He was awarded a
Nobel Prize
in 1906, "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases." He was
knighted
in 1908 and appointed to the
Order of Merit
in 1912. In 1914 he gave the
Romanes Lecture
in
Oxford
on "The atomic theory". In 1918 he became Master of
Trinity College
,
Cambridge
, where he remained until his death. He died on August 30, 1940 and was buried in
Westminster Abbey
, close to
Sir Isaac Newton
.
Thomson was elected a Fellow of the
Royal Society
[1]
on 12 June 1884 and was President of the Royal Society from 1915 to 1920.
Career[
edit
]
Discovery of the electron[
edit
]
Several scientists, such as
William Prout
and
Norman Lockyer
, had suggested that atoms were built up from a more fundamental unit, but they envisioned this unit to be the size of the smallest atom, hydrogen. Thomson, in 1897, was the first to suggest that the fundamental unit was over 1000 times smaller than an atom, suggesting the subatomic particles now known as electrons. Thomson discovered this through his explorations on the properties of
cathode rays
. Thomson made his suggestion on 30 April 1897 following his discovery that
Lenard rays
could travel much further through air than expected for an atom-sized particle.
[4]
He estimated the mass of cathode rays by measuring the heat generated when the rays hit a thermal junction and comparing this with the magnetic deflection of the rays. His experiments suggested not only that cathode rays were over 1000 times lighter than the hydrogen atom, but also that their mass was the same whatever type of atom they came from. He concluded that the rays were composed of very light, negatively charged particles which were a universal building block of atoms. He called the particles "corpuscles", but later scientists preferred the name
electron
which had been suggested by
George Johnstone Stoney
in 1891, prior to Thomson's actual discovery.
[5]
In April 1897 Thomson had only early indications that the cathode rays could be deflected electrically (previous investigators such as
Heinrich Hertz
had thought they could not be). A month after Thomson's announcement of the corpuscle he found that he could reliably deflect the rays by an electric field if he evacuated the discharge tube to a very low pressure. By comparing the deflection of a beam of cathode rays by electric and magnetic fields he obtained more robust measurements of the mass to charge ratio that confirmed his previous estimates.
[6]
This became the classic means of measuring the charge and mass of the electron.
Thomson believed that the corpuscles emerged from the atoms of the trace gas inside his
cathode ray tubes
. He thus concluded that atoms were divisible, and that the corpuscles were their building blocks. To explain the overall neutral charge of the atom, he proposed that the corpuscles were distributed in a uniform sea of positive charge; this was the "plum pudding" model—the electrons were embedded in the positive charge like plums in a plum pudding (although in Thomson's model they were not stationary, but orbiting rapidly
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