During the course of conduction of electricity through the gases in discharge tube at low pressure, it is found that a stage come entire tube was filled with darkness and in the end of the glass tube near the annode showed a tipical glow looking at this glow it was assumed that some sort of radiation comes out from cathode when an opic object like metalic cross was placed in between the cathode and annode its shadow was form towards the annode and this observation kaid J.J Thomson and his associated to reach a conclusion that some sort of invisible radiations are emited by cathode ray. The next step was to study the properties of the show cathode rays when a small padel made of mica was placed in between in cathode and annode. The padel started rotating this rotation indicated that there is something very minute invisible particles present in cathode ray.
When strong electric and magnetic field were applied one by one the deflection of cathode ray shows a confirmation that there is existence of negative charge. If this two experiment facts led to a conclusion that the cathode ray consist of stream of invisible negativity charged particles must originated from pre-existing material present in discharge tube that is gas present in the glass tube. To investigate this fact e/m of negatively charged particles present in the cathode rays was determined. Surprisingly the value of e/m was expansively very high. This led J.J Thomson to conclude the negatively charged particles in cathode rays were not of atomic or molecular origin.
The higher e/m suggested that the particles present in the cathode rays must be sub-atomic in origin which was against the indivisibility of atom to get a further confrigation this exp eriment done by using different gases and vapours of solid strikingly value of e/m was found to be invarability same this final result led J.J Thomson to purpose electron theory of matter. According to electron theory of matter, atom consist of a sub-atomic particles having negative charge. This negatively charged particles was given the name 'electron'. It's mass is about 1/1837 times the mass of hydrogen atom.
With the invent of electron theory of matter there came another question about the electrical nutriality of atom. To overcome this question with simple logic J J Thomson proposed Thomson's atom model according to this atom model, atom consist of a positively charge sphere in which negatively charge electrons are imbedded in it like the seeds of watermelon
Supplementry Information
Radioactive materials are those materials which emit positively charged 'Alpha' particles which mass 4U and charge 2e+ besides Alpha particles radioactive materials emit 'Beta' particle which are nothing but electrons along with this 'gamma' ray are given out which are highly energetic photons light particles. [ Alpha particles being massive compared to break open atoms. ] Rather ford in order to investigate the internal composition of atom. He devised and experiment called " Alpha particles scattering experiment " He use a thin gold foil held inside a circular collar of zinc sulphide screen when Alpha particles strike again zinc sulphide coated screen a blink of light is produced which can be seen with the help of microscope. The microscope is so adjusted that it can be fix a different angles around the zinc sulphide screen. The blink of light produced around the scintillation was counted with the help of mechanical counter.
I ) Ruther Ford observed that most of the Alpha particles pass through gold foil without any reflection.
II ) Few Alpha particles suffered a small angular daviation.
III ) Very very few on an average one out of twenty thousand Alpha particles suffered an angular daviation of 90° or more.
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