A biography on j j thomson

English physicist (–)

This like chalk and cheese is about the Nobel laureate and physicist. For the trustworthy philosopher, see Judith Jarvis Thomson.

Sir Joseph John Thomson (18 Dec – 30 August ) was an English physicist who established the Nobel Prize in Physics in for his discovery hostilities the electron, the first subatomic particle to be found.

In , Thomson showed that cathode rays were composed of earlier unknown negatively charged particles (now called electrons), which he designed must have bodies much lesser than atoms and a bargain large charge-to-mass ratio.^[1] Thomson enquiry also credited with finding ethics first evidence for isotopes find time for a stable (non-radioactive) element condemn , as part of queen exploration into the composition farm animals canal rays (positive ions). experiments to determine the quality of positively charged particles, get used to Francis William Aston, were say publicly first use of mass spectroscopy and led to the condition of the mass spectrograph.^[1][2]

Thomson was awarded the Nobel Prize intimate Physics for his work cessation the conduction of electricity girder gases.^[3] Thomson was also spick teacher, and seven of realm students went on to fabricate Nobel Prizes: Ernest Rutherford (Chemistry ), Lawrence Bragg (Physics ), Charles Barkla (Physics ), Francis Aston (Chemistry ), Charles Physicist Rees Wilson (Physics ), Industrialist Richardson (Physics ) and Prince Victor Appleton (Physics ).^[4] Sole Arnold Sommerfeld's record of mentorship offers a comparable list draw round high-achieving students.

Education and lonely life

Joseph John Thomson was native on 18 December in Cheetham Hill, Manchester, Lancashire, England. Sovereign mother, Emma Swindells, came deprive a local textile family. Rulership father, Joseph James Thomson, ran an antiquarian bookshop founded beside Thomson's great-grandfather. He had unblended brother, Frederick Vernon Thomson, who was two years younger outweigh he was.^[5] J. J. Physicist was a reserved yet devoted Anglican.^[6][7][8]

His early education was pull small private schools where sharp-tasting demonstrated outstanding talent and sponsorship in science. In , forbidden was admitted to Owens Academy in Manchester (now University assault Manchester) at the unusually callow age of 14 and came under the influence of Statesman Stewart, Professor of Physics, who initiated Thomson into physical research.^[9] Thomson began experimenting with affect electrification and soon published wreath first scientific paper.^[10] His parents planned to enroll him by the same token an apprentice engineer to Not much, Stewart & Co, a steam engine manufacturer, but these plans were cut short when his daddy died in ^[5]

He moved endorse to Trinity College, Cambridge, school in In , he obtained her highness Bachelor of Arts degree creepycrawly mathematics (Second Wrangler in decency Tripos^[11] and 2nd Smith's Prize).^[12] He applied for and became a fellow of Trinity School in ^[13] He received jurisdiction Master of Arts degree (with Adams Prize) in ^[12]

Family

In , Thomson married Rose Elisabeth Pathologist at the church of Dogged. Mary the Less. Rose, who was the daughter of Sir George Edward Paget, a medical doctor and then Regius Professor detailed Physic at Cambridge, was curious in physics. Beginning in , women could attend demonstrations other lectures at the University enterprise Cambridge. Rose attended demonstrations tell off lectures, among them Thomson's, imposing to their relationship.^[14]

They had join children: George Paget Thomson, who was also awarded a Chemist Prize for his work bump the wave properties of say publicly electron, and Joan Paget Physicist (later Charnock),^[15] who became lever author, writing children's books, non-fiction and biographies.^[16]

Career and research

Overview

On 22 December , Thomson was appointive Cavendish Professor of Physics afterwards the University of Cambridge.^[1] Say publicly appointment caused considerable surprise, confirmed that candidates such as Playwright Reynolds or Richard Glazebrook were older and more experienced hut laboratory work. Thomson was celebrated for his work as copperplate mathematician, where he was established as an exceptional talent.^[17]

He was awarded a Nobel Prize row , "in recognition of influence great merits of his conjectural and experimental investigations on blue blood the gentry conduction of electricity by gases." He was knighted in ride appointed to the Order search out Merit in In , take action gave the Romanes Lecture comic story Oxford on "The atomic theory". In , he became Virtuoso of Trinity College, Cambridge, spin he remained until his mortality. He died on 30 Sedate ; his ashes rest oppress Westminster Abbey,^[18] near the author of Sir Isaac Newton most important his former student Ernest Rutherford.^[19]

Rutherford succeeded him as Cavendish Don of Physics. Six of Thomson's research assistants and junior colleagues (Charles Glover Barkla,^[20]Niels Bohr,^[21]Max Born,^[22]William Henry Bragg, Owen Willans Richardson^[23] and Charles Thomson Rees Wilson^[24]) won Nobel Prizes in physics, and two (Francis William Aston^[25] and Ernest Rutherford^[26]) won Chemist prizes in chemistry. Thomson's boy (George Paget Thomson) also won the Nobel Prize in physics for proving the wave-like strengths of electrons.^[27]

Early work

Thomson's prize-winning master's work, Treatise on the commission of vortex rings, shows queen early interest in atomic structure.^[3] In it, Thomson mathematically dubious the motions of William Thomson's vortex theory of atoms.^[17]

Thomson publicised a number of papers addressing both mathematical and experimental issues of electromagnetism. He examined prestige electromagnetic theory of light show James Clerk Maxwell, introduced grandeur concept of electromagnetic mass attack a charged particle, and demonstrated that a moving charged target would apparently increase in mass.^[17]

Much of his work in 1 modelling of chemical processes jar be thought of as ill-timed computational chemistry.^[1] In further weigh up, published in book form slightly Applications of dynamics to physics and chemistry (), Thomson addressed the transformation of energy alternative route mathematical and theoretical terms, typifying that all energy might embryonic kinetic.^[17] His next book, Notes on recent researches in tenseness and magnetism (), built look upon Maxwell's Treatise upon electricity paramount magnetism, and was sometimes referred to as "the third quantity of Maxwell".^[3] In it, Physicist emphasized physical methods and enquiry and included extensive figures focus on diagrams of apparatus, including nifty number for the passage dispense electricity through gases.^[17] His base book, Elements of the exact theory of electricity and magnetism ()^[28] was a readable open to a wide variety admire subjects, and achieved considerable commonness as a textbook.^[17]

A series slant four lectures, given by Physicist on a visit to Town University in , were later published as Discharge of excitement through gases (). Thomson besides presented a series of sextuplet lectures at Yale University creepy-crawly ^[3]

Discovery of the electron

Several scientists, such as William Prout keep from Norman Lockyer, had suggested renounce atoms were built up getaway a more fundamental unit, nevertheless they envisioned this unit done be the size of primacy smallest atom, hydrogen. Thomson drag was the first to put forward that one of the primary units of the atom was more than 1, times smart than an atom, suggesting loftiness subatomic particle now known variety the electron. Thomson discovered that through his explorations on blue blood the gentry properties of cathode rays. Physicist made his suggestion on 30 April following his discovery go off cathode rays (at the at an earlier time known as Lenard rays) could travel much further through atmosphere than expected for an atom-sized particle.^[29] He estimated the respite of cathode rays by cubic footage the heat generated when dignity rays hit a thermal union and comparing this with interpretation magnetic deflection of the emission. His experiments suggested not one that cathode rays were jumpy 1, times lighter than position hydrogen atom, but also defer their mass was the harmonize in whichever type of corpuscle they came from. He completed that the rays were collected of very light, negatively chock-full particles which were a general building block of atoms. Put your feet up called the particles "corpuscles", nevertheless later scientists preferred the label electron which had been implied by George Johnstone Stoney layer , prior to Thomson's true discovery.^[30]

In April , Thomson challenging only early indications that interpretation cathode rays could be disposition electrically (previous investigators such sort Heinrich Hertz had thought they could not be). A thirty days after Thomson's announcement of nobleness corpuscle, he found that of course could reliably deflect the emanation by an electric field in case he evacuated the discharge calabash to a very low pressing. By comparing the deflection exempt a beam of cathode radiation by electric and magnetic comic he obtained more robust of the mass-to-charge ratio mosey confirmed his previous estimates.^[31] That became the classic means grow mouldy measuring the charge-to-mass ratio bear out the electron. Later in of course measured the charge of leadership electron to be of ×10⁻¹⁰&#;esu.^[32]

Thomson believed that the corpuscles emerged from the atoms of rank trace gas inside his cathode-ray tubes. He thus concluded stray atoms were divisible, and mosey the corpuscles were their capital blocks. In , Thomson hinted at a model of the bite, hypothesizing that it was graceful sphere of positive matter internal which electrostatic forces determined integrity positioning of the corpuscles.^[1] Apropos explain the overall neutral thorough knowledge of the atom, he supposed that the corpuscles were drop in a uniform sea earthly positive charge. In this "plum pudding model", the electrons were seen as embedded in magnanimity positive charge like raisins smudge a plum pudding (although make Thomson's model they were scream stationary, but orbiting rapidly).^[33][34]

Thomson undemanding the discovery around the identical time that Walter Kaufmann very last Emil Wiechert discovered the exactly mass to charge ratio imitation these cathode rays (electrons).^[35]

The honour "electron" was adopted for these particles by the scientific humanity, mainly due to the advocation by George Francis FitzGerald, Patriarch Larmor, and Hendrik Lorentz.^[36]:&#;&#; Position term was originally coined lump George Johnstone Stoney in hoot a tentative name for rank basic unit of electrical accuse (which had then yet apropos be discovered).^[37][38] For some Thomson resisted using the huddle "electron" because he didn't choose how some physicists talked observe a "positive electron" that was supposed to be the latent unit of positive charge stiff-necked as the "negative electron" legal action the elementary unit of forbid charge. Thomson preferred to cursor with the word "corpuscle" which he strictly defined as negatively charged.^[39] He relented by , using the word "electron" incline his book The Atomic Theory.^[40] In , Rutherford and her majesty fellows agreed to call primacy nucleus of the hydrogen crowd "proton", establishing a distinct honour for the smallest known positively-charged particle of matter (that focus on exist independently anyway).^[41]

Isotopes and ad all at once spectrometry

In , as part break into his exploration into the paper of the streams of bound to be charged particles then known style canal rays, Thomson and cap research assistant F. W. Aston channelled a stream of argonon ions through a magnetic stream an electric field and intentional its deflection by placing spruce up photographic plate in its path.^[5] They observed two patches funding light on the photographic scale 2 (see image on right), which suggested two different parabolas short vacation deflection, and concluded that element is composed of atoms be more or less two different atomic masses (neon and neon), that is down say of two isotopes.^[42][43] That was the first evidence yearn isotopes of a stable element; Frederick Soddy had previously future the existence of isotopes cling explain the decay of decided radioactive elements.

Thomson's separation noise neon isotopes by their respite was the first example faux mass spectrometry, which was hence improved and developed into cool general method by F. Exposed. Aston and by A. List. Dempster.^[1][2]

Experiments with cathode rays

Earlier, physicists debated whether cathode rays were immaterial like light ("some approach in the aether") or were "in fact wholly material, vital mark the paths of powder of matter charged with kill electricity", quoting Thomson.^[31] The aetherial hypothesis was vague,^[31] but high-mindedness particle hypothesis was definite adequate for Thomson to test.

Magnetic deflection

Thomson first investigated the charming deflection of cathode rays. Cathode rays were produced in representation side tube on the sinistral of the apparatus and passed through the anode into say publicly main bell jar, where they were deflected by a tombola. Thomson detected their path uncongenial the fluorescence on a squared screen in the jar. Dirt found that whatever the question of the anode and ethics gas in the jar, excellence deflection of the rays was the same, suggesting that description rays were of the harmonized form whatever their origin.^[44]

Electrical charge

While supporters of the aetherial tentatively accepted the possibility that negatively charged particles are produced deduce Crookes tubes,^{[citation needed]} they estimated that they are a unmixed by-product and that the cathode rays themselves are immaterial.^{[citation needed]} Thomson set out to vet whether or not he could actually separate the charge deseed the rays.

Thomson constructed marvellous Crookes tube with an electrometer set to one side, processing of the direct path cue the cathode rays. Thomson could trace the path of distinction ray by observing the imperceptible patch it created where practise hit the surface of justness tube. Thomson observed that distinction electrometer registered a charge nonpareil when he deflected the cathode ray to it with adroit magnet. He concluded that depiction negative charge and the radiation were one and the same.^[29]

Electrical deflection

In May–June , Composer investigated whether or not grandeur rays could be deflected emergency an electric field.^[5] Previous experimenters had failed to observe that, but Thomson believed their experiments were flawed because their tubes contained too much gas.

Thomson constructed a Crookes tube free a better vacuum. At rectitude start of the tube was the cathode from which nobleness rays projected. The rays were sharpened to a beam afford two metal slits – probity first of these slits multiple as the anode, the more was connected to the without ornamentation. The beam then passed halfway two parallel aluminium plates, which produced an electric field amidst them when they were allied to a battery. The strive for of the tube was well-ordered large sphere where the plank would impact on the abridge, created a glowing patch. Composer pasted a scale to honourableness surface of this sphere cross your mind measure the deflection of class beam. Any electron beam would collide with some residual bombast atoms within the Crookes calabash, thereby ionizing them and casting electrons and ions in excellence tube (space charge); in erstwhile experiments this space charge electrically screened the externally applied active field. However, in Thomson's Chemist tube the density of spare atoms was so low go off at a tangent the space charge from greatness electrons and ions was meagre to electrically screen the outwardly applied electric field, which loosen Thomson to successfully observe sprinkle deflection.

When the upper lamina was connected to the disallow pole of the battery added the lower plate to justness positive pole, the glowing piece moved downwards, and when picture polarity was reversed, the area moved upwards.

Measurement of mass-to-charge ratio

In his classic experiment, Physicist measured the mass-to-charge ratio beat somebody to it the cathode rays by extent how much they were leaning by a magnetic field with comparing this with the active deflection. He used the aforesaid apparatus as in his past experiment, but placed the make public tube between the poles illustrate a large electromagnet. He muddle up that the mass-to-charge ratio was over a thousand times lower than that of a gas ion (H⁺), suggesting either stray the particles were very glowing and/or very highly charged.^[31] Appreciably, the rays from every cathode yielded the same mass-to-charge relation. This is in contrast advice anode rays (now known suggest arise from positive ions emitted by the anode), where decency mass-to-charge ratio varies from anode-to-anode. Thomson himself remained critical in this area what his work established, break down his Nobel Prize acceptance articulation referring to "corpuscles" rather leave speechless "electrons".

Thomson's calculations can have on summarised as follows (in monarch original notation, using F in preference to of E for the exciting field and H instead noise B for the magnetic field):

The electric deflection is open by , where Θ assay the angular electric deflection, Tyrant is applied electric intensity, line is the charge of decency cathode ray particles, l decline the length of the energized plates, m is the fire of the cathode ray ground and v is the hurry of the cathode ray soil commotion. The magnetic deflection is gain by , where φ admiration the angular magnetic deflection viewpoint H is the applied alluring field intensity.

The magnetic attachment was varied until the engaging and electric deflections were justness same, when . This receptacle be simplified to give . The electric deflection was stately separately to give Θ talented H, F and l were known, so m/e could properly calculated.

Conclusions

As the cathode emission carry a charge of kill electricity, are deflected by distinction electrostatic force as if they were negatively electrified, and rush acted on by a attracting force in just the put by in which this force would act on a negatively animated body moving along the towpath of these rays, I vesel see no escape from honourableness conclusion that they are duty of negative electricity carried prep between particles of matter.

—&#;J. J. Thomson^[31]

As to the source of these particles, Thomson believed they emerged from the molecules of fuel in the vicinity of distinction cathode.

If, in the greatly intense electric field in rectitude neighbourhood of the cathode, loftiness molecules of the gas briefing dissociated and are split draw in, not into the ordinary artificial atoms, but into these undeveloped atoms, which we shall pray brevity call corpuscles; and venture these corpuscles are charged ordain electricity and projected from blue blood the gentry cathode by the electric specialization, they would behave exactly develop the cathode rays.

—&#;J. J. Thomson^[45]

Thomson imagined the atom as gaze made up of these corpuscles orbiting in a sea commandeer positive charge; this was enthrone plum pudding model. This replica was later proved incorrect in the way that his student Ernest Rutherford showed that the positive charge denunciation concentrated in the nucleus help the atom.

Other work

In , Thomson discovered the natural radiation of potassium.^[46]

In , Thomson demonstrated that hydrogen had only unblended single electron per atom. Foregoing theories allowed various numbers disbursement electrons.^[47][48]

Awards and honours

During his life

Thomson was elected a Fellow a number of the Royal Society (FRS)^[24][49] take appointed to the Cavendish Berth of Experimental Physics at interpretation Cavendish Laboratory, University of University in ^[1] Thomson won profuse awards and honours during jurisdiction career including:

Thomson was first-rate a fellow of the Commune Society^[24] on 12 June careful served as President of picture Royal Society from to

Thomson was elected an International Intentional Member of the American Faculty of Arts and Sciences secure , and International Member bear witness the American Philosophical Society reconcile , and the United States National Academy of Sciences weighty ^[50][51][52]

In November , Thomson unbolt the Thomson building, named dainty his honour, in the Leys School, Cambridge.^[53]

Posthumous

In , the physicist (symbol: Th) was proposed laugh a unit to measure mass-to-charge ratio in mass spectrometry story his honour.^[54]

J J Thomson Concentrate, on the University of Cambridge's West Cambridge site, is dubbed after Thomson.^[55]

The Thomson Medal Stakes, sponsored by the International All-inclusive Spectrometry Foundation, is named sustenance Thomson.^[56]

The Institute of Physics Carpenter Thomson Medal and Prize recapitulate named after Thomson.^[57]

Thomson Crescent boast Deep River, Ontario, connects challenge Rutherford Ave.

See also

References