what is the significance of the determination of the q/m ratio by thomson? i know its shows cathode rays have a particulate nature but why?? ive searched other posts and they said sometinh about electrons being very small and have a tiny mass... i dont get this, help please!
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significance of the q/m ratio (1 Viewer)
- Thread starter Arithela
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hollyy.
stop looking at me swan.
ok.
q/m = 1.76x10^-11
this means that either the charge is really big
or the mass is really small
thomson went with the second option betcause to have a really big charge would be stupid because things would be attracting and repelling all over the place
but in thonsons time it was considered that the smallest thing was the hydrogen atom
accord to his theory the cathode ray (electron) is 1800 times smaller than the hydrogen atom -- which contradicted common belief.
therefore he was ridiculed for a long time
thus the ratio is significant as it altered common belief about what the smallest particle
hope this helps
q/m = 1.76x10^-11
this means that either the charge is really big
or the mass is really small
thomson went with the second option betcause to have a really big charge would be stupid because things would be attracting and repelling all over the place
but in thonsons time it was considered that the smallest thing was the hydrogen atom
accord to his theory the cathode ray (electron) is 1800 times smaller than the hydrogen atom -- which contradicted common belief.
therefore he was ridiculed for a long time
thus the ratio is significant as it altered common belief about what the smallest particle
hope this helps
Here's a section of notes our teacher gave our class:
Thomson suggested that, since all the materials tested produced cathode rays with exactly the same q/m ratio, the Dalton model of the atom was incorrect and atoms were not indivisible. He proposed that atoms are made of smaller elementary particles, one being the building blocks of the cathode rays. These building blocks were identified as electrons.
The charge to mass ratio of hydrogen ions was also measured by using experiments involving electrolysis. This ratio is only 9.6x10^7 C kg-1.
The fact that the q/m ratio of an electron is about 1800 times larger than the q/m ratio of a hydrogen ion can be interpreted in two ways:
1. the charge on the electron is much greater than the charge on the hydrogen ion, or
2. the mass of the ion is much greater than the mass of the electron
Thomson suggested a new atomic model - since materials are not normally electrically charged, atoms must be neutral as well. He knew that the atoms can emit negative electrons and he also knew about the existence of positive ions. Thomson proposed that atoms were tiny positive spheres containing even tinier negative electrons, and was able to explain some of the properties of matter with this model. This model of the atom was called the 'plum pudding' model
I thought we only had to outline Thomson's experiment to measure the charge/mass ratio of an electron, which just means saying what he did and deriving the formula, but I hope this helps anyway
Thomson suggested that, since all the materials tested produced cathode rays with exactly the same q/m ratio, the Dalton model of the atom was incorrect and atoms were not indivisible. He proposed that atoms are made of smaller elementary particles, one being the building blocks of the cathode rays. These building blocks were identified as electrons.
The charge to mass ratio of hydrogen ions was also measured by using experiments involving electrolysis. This ratio is only 9.6x10^7 C kg-1.
The fact that the q/m ratio of an electron is about 1800 times larger than the q/m ratio of a hydrogen ion can be interpreted in two ways:
1. the charge on the electron is much greater than the charge on the hydrogen ion, or
2. the mass of the ion is much greater than the mass of the electron
Thomson suggested a new atomic model - since materials are not normally electrically charged, atoms must be neutral as well. He knew that the atoms can emit negative electrons and he also knew about the existence of positive ions. Thomson proposed that atoms were tiny positive spheres containing even tinier negative electrons, and was able to explain some of the properties of matter with this model. This model of the atom was called the 'plum pudding' model
I thought we only had to outline Thomson's experiment to measure the charge/mass ratio of an electron, which just means saying what he did and deriving the formula, but I hope this helps anyway
Forbidden.
Banned
Actually peeps, Thomson's experiment was a variation of a mass spectrometer (namely the Bainbridge mass spectrometer) which separates ions according to their charge-per-mass ratio.Seamus733 said:Here's a section of notes our teacher gave our class:
Thomson suggested that, since all the materials tested produced cathode rays with exactly the same q/m ratio, the Dalton model of the atom was incorrect and atoms were not indivisible. He proposed that atoms are made of smaller elementary particles, one being the building blocks of the cathode rays. These building blocks were identified as electrons.
The charge to mass ratio of hydrogen ions was also measured by using experiments involving electrolysis. This ratio is only 9.6x10^7 C kg-1.
The fact that the q/m ratio of an electron is about 1800 times larger than the q/m ratio of a hydrogen ion can be interpreted in two ways:
1. the charge on the electron is much greater than the charge on the hydrogen ion, or
2. the mass of the ion is much greater than the mass of the electron
Thomson suggested a new atomic model - since materials are not normally electrically charged, atoms must be neutral as well. He knew that the atoms can emit negative electrons and he also knew about the existence of positive ions. Thomson proposed that atoms were tiny positive spheres containing even tinier negative electrons, and was able to explain some of the properties of matter with this model. This model of the atom was called the 'plum pudding' model
I thought we only had to outline Thomson's experiment to measure the charge/mass ratio of an electron, which just means saying what he did and deriving the formula, but I hope this helps anyway
Thomson instead used a cathode ray tube to perform his experiment to find the q/m ratio (or ee/m) for electrons.
Also, the results of this crucial experiment represent the discovery of the electron as a fundamental particle of nature (remember this !) as mentioned by a descendant of Frank Jewett Jr., who worked with J.J. Thomson in the actual experiment.
Otherwise you've pretty much answered what the thread starter asked.
Last edited:
Captain Gh3y
Rhinorhondothackasaurus
the most important thing was that it allowed us to calculate the mass of an electron
the charge came from Milikan's oil drop experiment
the charge came from Milikan's oil drop experiment
ngogiathuan
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From my understanding, the significance of the ratio q/m simply is that it suggests that the rays must have a charge, and a mass ( q and m), so the ray must be particle (instead of being wave)
Correct me if im wrong
Correct me if im wrong
kooltrainer
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yeh, there was a dilemma about cathode rays being a wave or particle.. thompson found its charge to mass ration ended this debate because light cant have a mass .. it therefore must be a particlengogiathuan said:
J.J Thomson’s Experiment to determine the charge to mass ratio of cathode rays (q/m)
J.J Thomson set up an experiment where cathode rays could be passed through both an electric field and an electric field at the same time.
He was able to adjust the strengths of the fields so that their opposite effects exactly cancelled out, and the cathode ray beam hit the fluorescent screen in the centre. At this point the force due to the electric field was equal to the force due to the magnetic field. He was then able to determine the strengths of the fields using the currents and voltages applied. Using this he was able to determine the charge to mass ratio (q/m).
This was a vital piece of information for scientists, as it was now established beyond doubt that cathode rays were particles and not waves. Scientists now knew that the atom was made up of smaller parts one of which was the “cathode ray particle” soon re-named the ELECTRON.
-->J.J Thomson indeed found that cathode rays DO bend in an electric field
-->The most crucial result of this experiment was that it proved that atoms were made up of smaller particles, one of which was the ELECTRON
J.J Thomson set up an experiment where cathode rays could be passed through both an electric field and an electric field at the same time.
He was able to adjust the strengths of the fields so that their opposite effects exactly cancelled out, and the cathode ray beam hit the fluorescent screen in the centre. At this point the force due to the electric field was equal to the force due to the magnetic field. He was then able to determine the strengths of the fields using the currents and voltages applied. Using this he was able to determine the charge to mass ratio (q/m).
This was a vital piece of information for scientists, as it was now established beyond doubt that cathode rays were particles and not waves. Scientists now knew that the atom was made up of smaller parts one of which was the “cathode ray particle” soon re-named the ELECTRON.
-->J.J Thomson indeed found that cathode rays DO bend in an electric field
-->The most crucial result of this experiment was that it proved that atoms were made up of smaller particles, one of which was the ELECTRON