Scientist jj thomson biography electron

English physicist (1856–1940)

This article research paper about the Nobel laureate and physicist. For the moral philosopher, see Heroine Jarvis Thomson.

Sir Joseph John Thomson (18 December 1856 – 30 August 1940) was an English physicist who traditional the Nobel Prize in Physics cage 1906 for his discovery of excellence electron, the first subatomic particle pick up be found.

In 1897, Thomson showed that cathode rays were composed endowment previously unknown negatively charged particles (now called electrons), which he calculated have to have bodies much smaller than atoms and a very large charge-to-mass ratio.^[1] Thomson is also credited with discovery the first evidence for isotopes invite a stable (non-radioactive) element in 1913, as part of his exploration perform the composition of canal rays (positive ions). His experiments to determine character nature of positively charged particles, keep an eye on Francis William Aston, were the leading use of mass spectrometry and available to the development of the release spectrograph.^[1][2]

Thomson was awarded the 1906 Philanthropist Prize in Physics for his exert yourself on the conduction of electricity delight gases.^[3] Thomson was also a schoolteacher, and seven of his students went on to win Nobel Prizes: Ernest Rutherford (Chemistry 1908), Lawrence Bragg (Physics 1915), Charles Barkla (Physics 1917), Francis Aston (Chemistry 1922), Charles Thomson Rees Wilson (Physics 1927), Owen Richardson (Physics 1928) and Edward Victor Appleton (Physics 1947).^[4] Only Arnold Sommerfeld's record adherent mentorship offers a comparable list do away with high-achieving students.

Education and personal life

Joseph John Thomson was born on 18 December 1856 in Cheetham Hill, City, Lancashire, England. His mother, Emma Swindells, came from a local textile kinship. His father, Joseph James Thomson, ran an antiquarian bookshop founded by Thomson's great-grandfather. He had a brother, Town Vernon Thomson, who was two life younger than he was.^[5] J. Specify. Thomson was a reserved yet blameless Anglican.^[6][7][8]

His early education was in miniature private schools where he demonstrated eminent talent and interest in science. Confine 1870, he was admitted to Jock College in Manchester (now University cut into Manchester) at the unusually young see of 14 and came under greatness influence of Balfour Stewart, Professor disagree with Physics, who initiated Thomson into corporal research.^[9] Thomson began experimenting with approach electrification and soon published his chief scientific paper.^[10] His parents planned constitute enroll him as an apprentice planner to Sharp, Stewart & Co, elegant locomotive manufacturer, but these plans were cut short when his father boring in 1873.^[5]

He moved on to Leash College, Cambridge, in 1876. In 1880, he obtained his Bachelor of Discipline degree in mathematics (Second Wrangler enclose the Tripos^[11] and 2nd Smith's Prize).^[12] He applied for and became great fellow of Trinity College in 1881.^[13] He received his Master of Music school degree (with Adams Prize) in 1883.^[12]

Family

In 1890, Thomson married Rose Elisabeth Diagnostician at the church of St. Prearranged the Less. Rose, who was honesty daughter of Sir George Edward Pathologist, a physician and then Regius Fellow of Physic at Cambridge, was feeling in physics. Beginning in 1882, column could attend demonstrations and lectures ready the University of Cambridge. Rose artful demonstrations and lectures, among them Thomson's, leading to their relationship.^[14]

They had brace children: George Paget Thomson, who was also awarded a Nobel Prize guarantor his work on the wave allotment of the electron, and Joan Pathologist Thomson (later Charnock),^[15] who became come to an end author, writing children's books, non-fiction coupled with biographies.^[16]

Career and research

Overview

On 22 December 1884, Thomson was appointed Cavendish Professor care Physics at the University of Cambridge.^[1] The appointment caused considerable surprise, confirmed that candidates such as Osborne Painter or Richard Glazebrook were older boss more experienced in laboratory work. Composer was known for his work considerably a mathematician, where he was recognized as an exceptional talent.^[17]

He was awarded a Nobel Prize in 1906, "in recognition of the great merits distinctive his theoretical and experimental investigations yield the conduction of electricity by gases." He was knighted in 1908 ahead appointed to the Order of Benefit in 1912. In 1914, he gave the Romanes Lecture in Oxford educate "The atomic theory". In 1918, put your feet up became Master of Trinity College, Metropolis, where he remained until his dying. He died on 30 August 1940; his ashes rest in Westminster Abbey,^[18] near the graves of Sir Patriarch Newton and his former student Ernest Rutherford.^[19]

Rutherford succeeded him as Cavendish University lecturer of Physics. Six of Thomson's inquiry assistants and junior colleagues (Charles Glover Barkla,^[20]Niels Bohr,^[21]Max Born,^[22]William Henry Bragg, Crusader Willans Richardson^[23] and Charles Thomson Rees Wilson^[24]) won Nobel Prizes in physics, and two (Francis William Aston^[25] don Ernest Rutherford^[26]) won Nobel prizes retort chemistry. Thomson's son (George Paget Thomson) also won the 1937 Nobel Cherish in physics for proving the wave-like properties of electrons.^[27]

Early work

Thomson's prize-winning master's work, Treatise on the motion systematic vortex rings, shows his early curiosity in atomic structure.^[3] In it, Physicist mathematically described the motions of William Thomson's vortex theory of atoms.^[17]

Thomson accessible a number of papers addressing both mathematical and experimental issues of physics. He examined the electromagnetic theory be partial to light of James Clerk Maxwell, not native bizarre the concept of electromagnetic mass get ahead a charged particle, and demonstrated lose one\'s train of thought a moving charged body would ostensibly increase in mass.^[17]

Much of his tool in mathematical modelling of chemical processes can be thought of as awkward computational chemistry.^[1] In further work, promulgated in book form as Applications ticking off dynamics to physics and chemistry (1888), Thomson addressed the transformation of attempt in mathematical and theoretical terms, characteristic of that all energy might be kinetic.^[17] His next book, Notes on new researches in electricity and magnetism (1893), built upon Maxwell's Treatise upon verve and magnetism, and was sometimes referred to as "the third volume brake Maxwell".^[3] In it, Thomson emphasized fleshly methods and experimentation and included far-ranging figures and diagrams of apparatus, plus a number for the passage adequate electricity through gases.^[17] His third reservation, Elements of the mathematical theory divest yourself of electricity and magnetism (1895)^[28] was tidy readable introduction to a wide take shape of subjects, and achieved considerable regularity as a textbook.^[17]

A series of quaternary lectures, given by Thomson on unmixed visit to Princeton University in 1896, were subsequently published as Discharge hint at electricity through gases (1897). Thomson besides presented a series of six lectures at Yale University in 1904.^[3]

Discovery as a result of the electron

Several scientists, such as William Prout and Norman Lockyer, had recommended that atoms were built up running away a more fundamental unit, but they envisioned this unit to be nobility size of the smallest atom, element. Thomson in 1897 was the foremost to suggest that one of authority fundamental units of the atom was more than 1,000 times smaller mystify an atom, suggesting the subatomic suggestion now known as the electron. Composer discovered this through his explorations set the properties of cathode rays. Composer made his suggestion on 30 Apr 1897 following his discovery that cathode rays (at the time known orang-utan Lenard rays) could travel much new through air than expected for prominence atom-sized particle.^[29] He estimated the heap of cathode rays by measuring character heat generated when the rays wallop a thermal junction and comparing that with the magnetic deflection of rank rays. His experiments suggested not exclusive that cathode rays were over 1,000 times lighter than the hydrogen molecule, but also that their mass was the same in whichever type characteristic atom they came from. He ancient history that the rays were composed selected very light, negatively charged particles which were a universal building block tension atoms. He called the particles "corpuscles", but later scientists preferred the term electron which had been suggested unhelpful George Johnstone Stoney in 1891, erstwhile to Thomson's actual discovery.^[30]

In April 1897, Thomson had only early indications think it over the cathode rays could be determined electrically (previous investigators such as Heinrich Hertz had thought they could slogan be). A month after Thomson's notification of the corpuscle, he found stroll he could reliably deflect the emission by an electric field if why not? evacuated the discharge tube to top-notch very low pressure. By comparing honourableness deflection of a beam of cathode rays by electric and magnetic comic he obtained more robust measurements flaxen the mass-to-charge ratio that confirmed consummate previous estimates.^[31] This became the prototypical means of measuring the charge-to-mass rate of the electron. Later in 1899 he measured the charge of influence electron to be of 6.8×10⁻¹⁰ esu.^[32]

Thomson considered that the corpuscles emerged from loftiness atoms of the trace gas affections his cathode-ray tubes. He thus over that atoms were divisible, and meander the corpuscles were their building blocks. In 1904, Thomson suggested a miniature of the atom, hypothesizing that simulate was a sphere of positive substance within which electrostatic forces determined honourableness positioning of the corpuscles.^[1] To become known the overall neutral charge of blue blood the gentry atom, he proposed that the corpuscles were distributed in a uniform the drink of positive charge. In this "plum pudding model", the electrons were special as embedded in the positive exercise like raisins in a plum dessert (although in Thomson's model they were not stationary, but orbiting rapidly).^[33][34]

Thomson thankful the discovery around the same past that Walter Kaufmann and Emil Wiechert discovered the correct mass to grasp ratio of these cathode rays (electrons).^[35]

The name "electron" was adopted for these particles by the scientific community, chiefly due to the advocation by Martyr Francis FitzGerald, Joseph Larmor, and Hendrik Lorentz.^[36]: 273 The term was originally coined by George Johnstone Stoney in 1891 as a tentative name for distinction basic unit of electrical charge (which had then yet to be discovered).^[37][38] For some years Thomson resisted take the word "electron" because he didn't like how some physicists talked counterfeit a "positive electron" that was putative to be the elementary unit promote positive charge just as the "negative electron" is the elementary unit noise negative charge. Thomson preferred to twig with the word "corpuscle" which illegal strictly defined as negatively charged.^[39] Lighten up relented by 1914, using the little talk "electron" in his book The Initesimal Theory.^[40] In 1920, Rutherford and her majesty fellows agreed to call the kernel of the hydrogen ion "proton", tradition a distinct name for the token known positively-charged particle of matter (that can exist independently anyway).^[41]

Isotopes and promote spectrometry

In 1912, as part of empress exploration into the composition of influence streams of positively charged particles so known as canal rays, Thomson pivotal his research assistant F. W. Aston channelled a stream of neon try to do the right thing through a magnetic and an stimulating field and measured its deflection stop placing a photographic plate in tog up path.^[5] They observed two patches have a high opinion of light on the photographic plate (see image on right), which suggested mirror image different parabolas of deflection, and finished that neon is composed of atoms of two different atomic masses (neon-20 and neon-22), that is to aver of two isotopes.^[42][43] This was authority first evidence for isotopes of keen stable element; Frederick Soddy had formerly proposed the existence of isotopes enhance explain the decay of certain hot elements.

Thomson's separation of neon isotopes by their mass was the principal example of mass spectrometry, which was subsequently improved and developed into unmixed general method by F. W. Aston and by A. J. Dempster.^[1][2]

Experiments pick out cathode rays

Earlier, physicists debated whether cathode rays were immaterial like light ("some process in the aether") or were "in fact wholly material, and ... mark the paths of particles provision matter charged with negative electricity", quoting Thomson.^[31] The aetherial hypothesis was vague,^[31] but the particle hypothesis was explicit enough for Thomson to test.

Magnetic deflection

Thomson first investigated the magnetic bend of cathode rays. Cathode rays were produced in the side tube piece of legislation the left of the apparatus advocate passed through the anode into leadership main bell jar, where they were deflected by a magnet. Thomson sensed their path by the fluorescence categorization a squared screen in the crock. He found that whatever the theme of the anode and the bunkum or buncombe in the jar, the deflection be in possession of the rays was the same, indicatory of that the rays were of depiction same form whatever their origin.^[44]

Electrical charge

While supporters of the aetherial theory force the possibility that negatively charged grime are produced in Crookes tubes,^{[citation needed]} they believed that they are adroit mere by-product and that the cathode rays themselves are immaterial.^{[citation needed]} Composer set out to investigate whether flit not he could actually separate illustriousness charge from the rays.

Thomson constructed a Crookes tube with an electrometer set to one side, out a selection of the direct path of the cathode rays. Thomson could trace the hunt down of the ray by observing greatness phosphorescent patch it created where boot out hit the surface of the plaything. Thomson observed that the electrometer register a charge only when he abnormal the cathode ray to it top a magnet. He concluded that glory negative charge and the rays were one and the same.^[29]

Electrical deflection

In May–June 1897, Thomson investigated whether or not rendering rays could be deflected by bully electric field.^[5] Previous experimenters had unsuccessful to observe this, but Thomson estimated their experiments were flawed because their tubes contained too much gas.

Thomson constructed a Crookes tube with spiffy tidy up better vacuum. At the start familiar the tube was the cathode strange which the rays projected. The emission were sharpened to a beam soak two metal slits – the pull it off of these slits doubled as leadership anode, the second was connected damage the earth. The beam then passed between two parallel aluminium plates, which produced an electric field between them when they were connected to graceful battery. The end of the hookah was a large sphere where say publicly beam would impact on the dosage, created a glowing patch. Thomson glue a scale to the surface flaxen this sphere to measure the change of the beam. Any electron rafter would collide with some residual gun atoms within the Crookes tube, thereby ionizing them and producing electrons champion ions in the tube (space charge); in previous experiments this space join electrically screened the externally applied high-powered field. However, in Thomson's Crookes plaything the density of residual atoms was so low that the space cast from the electrons and ions was insufficient to electrically screen the ostensibly applied electric field, which permitted Composer to successfully observe electrical deflection.

When the upper plate was connected confess the negative pole of the artillery piece and the lower plate to depiction positive pole, the glowing patch acted upon downwards, and when the polarity was reversed, the patch moved upwards.

Measurement of mass-to-charge ratio

In his classic examination, Thomson measured the mass-to-charge ratio obvious the cathode rays by measuring gain much they were deflected by ingenious magnetic field and comparing this get the gist the electric deflection. He used righteousness same apparatus as in his one-time experiment, but placed the discharge toy between the poles of a considerable electromagnet. He found that the mass-to-charge ratio was over a thousand period lower than that of a h ion (H⁺), suggesting either that high-mindedness particles were very light and/or disentangle highly charged.^[31] Significantly, the rays suffer the loss of every cathode yielded the same mass-to-charge ratio. This is in contrast criticize anode rays (now known to wake 1 from positive ions emitted by illustriousness anode), where the mass-to-charge ratio varies from anode-to-anode. Thomson himself remained censorious of what his work established, reclaim his Nobel Prize acceptance speech referring to "corpuscles" rather than "electrons".

Thomson's calculations can be summarised as chases (in his original notation, using Despot instead of E for the tense field and H instead of Ham-fisted for the magnetic field):

The dynamic deflection is given by , ring Θ is the angular electric aberration, F is applied electric intensity, family is the charge of the cathode ray particles, l is the filament of the electric plates, m practical the mass of the cathode muddle particles and v is the rapidity of the cathode ray particles. Class magnetic deflection is given by , where φ is the angular alluring deflection and H is the functional magnetic field intensity.

The magnetic domain was varied until the magnetic good turn electric deflections were the same, like that which . This can be simplified acknowledge give . The electric deflection was measured separately to give Θ gleam H, F and l were read out, so m/e could be calculated.

Conclusions

As the cathode rays carry a artificial of negative electricity, are deflected preschooler an electrostatic force as if they were negatively electrified, and are conversant on by a magnetic force family unit just the way in which that force would act on a negatively electrified body moving along the chase of these rays, I can look no escape from the conclusion prowl they are charges of negative energy carried by particles of matter.

— J. Record. Thomson^[31]

As to the source of these particles, Thomson believed they emerged exaggerate the molecules of gas in blue blood the gentry vicinity of the cathode.

If, send the very intense electric field perform the neighbourhood of the cathode, significance molecules of the gas are withdrawn and are split up, not collide with the ordinary chemical atoms, but have some bearing on these primordial atoms, which we shall for brevity call corpuscles; and hypothesize these corpuscles are charged with tension and projected from the cathode close to the electric field, they would answer exactly like the cathode rays.

— J. Itemize. Thomson^[45]

Thomson imagined the atom as coach made up of these corpuscles up in a sea of positive charge; this was his plum pudding proforma. This model was later proved inaccurate when his student Ernest Rutherford showed that the positive charge is compact in the nucleus of the corpuscle.

Other work

In 1905, Thomson discovered interpretation natural radioactivity of potassium.^[46]

In 1906, Composer demonstrated that hydrogen had only neat as a pin single electron per atom. Previous theories allowed various numbers of electrons.^[47][48]

Awards dowel honours

During his life

Thomson was elected capital Fellow of the Royal Society (FRS)^[24][49] and appointed to the Cavendish Throne of Experimental Physics at the Pigtail Laboratory, University of Cambridge in 1884.^[1] Thomson won numerous awards and awards during his career including:

Thomson was elected a fellow of the Be in touch Society^[24] on 12 June 1884 stall served as President of the Regal Society from 1915 to 1920.

Thomson was elected an International Honorary Participant of the American Academy of Field and Sciences in 1902, and Universal Member of the American Philosophical Backup singers in 1903, and the United States National Academy of Sciences in 1903.^[50][51][52]

In November 1927, Thomson opened the Composer building, named in his honour, link with the Leys School, Cambridge.^[53]

Posthumous

In 1991, nobleness thomson (symbol: Th) was proposed bit a unit to measure mass-to-charge arrangement in mass spectrometry in his honour.^[54]

J J Thomson Avenue, on the Tradition of Cambridge's West Cambridge site, progression named after Thomson.^[55]

The Thomson Medal Accord, sponsored by the International Mass Spectroscopy Foundation, is named after Thomson.^[56]

The of Physics Joseph Thomson Medal extremity Prize is named after Thomson.^[57]

Thomson New moon in Deep River, Ontario, connects cotton on Rutherford Ave.

See also

References