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Jj thomson 2 [autosaved]
- 1. JJ ThomsonJJ Thomson kamilanowak@yahoo.comkamilanowak@yahoo.com By: Anthony, Carly, Amanda,By: Anthony, Carly, Amanda, Melissa, and KamilaMelissa, and Kamila
- 2. Background InfoBackground Info • English physicistEnglish physicist • Born:1856Born:1856 • Died:1940Died:1940 • Attended Cambridge University, thenAttended Cambridge University, then transferred to Owens College in 1870.transferred to Owens College in 1870. Became a lecturer after transferring toBecame a lecturer after transferring to third school, Trinity College.third school, Trinity College.
- 3. Perceived structurePerceived structure • JJ Thomson believed that atoms wereJJ Thomson believed that atoms were neutral and had no electric charge.neutral and had no electric charge. • He thought that electrons had a negativeHe thought that electrons had a negative charge.charge. • He thought that the atom is a sphericalHe thought that the atom is a spherical object that has electrons inside aobject that has electrons inside a homogeneous jellylike material.homogeneous jellylike material. Thompson’s perceived structure of atom
- 4. Perceived Structure Cont.Perceived Structure Cont. • He thought that it had a massive positiveHe thought that it had a massive positive charge distribution cancels out thecharge distribution cancels out the electrons.electrons. • Thomson's model is sometimes called aThomson's model is sometimes called a plum pudding model.plum pudding model. Thomson’s perceived structure of atom.
- 5. Postulate of the theoryPostulate of the theory • Thomson had theory that the ‘rays’ emitted from a electron gun wereThomson had theory that the ‘rays’ emitted from a electron gun were inseparable from the latent charge.inseparable from the latent charge. • Thomson had another theory that the rays carried a negativeThomson had another theory that the rays carried a negative charge.charge. Thomson's third theory was to try to work out the nature of theThomson's third theory was to try to work out the nature of the particles. They were too small to have their mass or chargeparticles. They were too small to have their mass or charge calculated directly, but he attempted to conclude this from howcalculated directly, but he attempted to conclude this from how much the particles were bent by electrical currents, of varyingmuch the particles were bent by electrical currents, of varying strengths.strengths.
- 6. Experimental DesignExperimental Design • First ExperimentFirst Experiment:: • His first experiment was to build a cathode ray tube withHis first experiment was to build a cathode ray tube with a metal cylinder on the end. This cylinder had two slits ina metal cylinder on the end. This cylinder had two slits in it, leading to electrometers, which could measure smallit, leading to electrometers, which could measure small electric charges. He found that when applying aelectric charges. He found that when applying a magnetic field across the tube, there was no activitymagnetic field across the tube, there was no activity made by the electrometers and so the charge had beenmade by the electrometers and so the charge had been bent away by the magnet. This proved that the negativebent away by the magnet. This proved that the negative charge and the ray were inseparable and intertwined.charge and the ray were inseparable and intertwined. First experiment Cathode Ray
- 7. Experimental Design Cont.Experimental Design Cont. • Experiment two:Experiment two: • For this, he made a slightly different cathode ray tube, with aFor this, he made a slightly different cathode ray tube, with a fluorescent coating at one end and a near perfect vacuum. Halfwayfluorescent coating at one end and a near perfect vacuum. Halfway down the tube were two electric plates, producing a positive and adown the tube were two electric plates, producing a positive and a negative charge, which he hoped would deflect the rays.negative charge, which he hoped would deflect the rays. • As he expected, the rays were deflected by the electric charge,As he expected, the rays were deflected by the electric charge, proving that the rays were made up of charged particles carrying aproving that the rays were made up of charged particles carrying a negative charge.negative charge. Second experiment Cathode Ray
- 8. Experimental Design Cont.Experimental Design Cont. • Experiment three:Experiment three: • Thomson decided to try to work out the nature of the particles.Thomson decided to try to work out the nature of the particles. • He found out that the mass to charge ratio was so high that theHe found out that the mass to charge ratio was so high that the particles either carried a huge charge, or were extremely small. Heparticles either carried a huge charge, or were extremely small. He came up with the idea that the cathode rays were made of particlescame up with the idea that the cathode rays were made of particles that came from the atoms themselves.that came from the atoms themselves. Third experiment Cathode Ray