Discovering e/m Ratio: The J.J. Thomson Experiment Explained

In summary, the e/m ratio is a physical constant that represents the ratio of an electron's charge to its mass. It was discovered by J.J. Thomson, a British physicist, through his experiments with cathode rays in 1897. By manipulating magnetic fields and voltage, Thomson was able to calculate the e/m ratio, providing evidence for the existence of electrons and their charge-to-mass ratio. This discovery had major implications for our understanding of atomic structure and paved the way for further discoveries in particle physics. Since Thomson's experiment, the e/m ratio has been refined and measured using various techniques, leading to a better understanding of the fundamental properties of matter.
  • #1
M. next
382
0
This experiment aims towards finding e/m ratio and it is a very well known experiment that's why I will directly post my question. Why do we evacuate the glass tube?
 
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  • #2
electrons would be easily stopped in a tube containing gas.
 
  • #3
M. next said:
Why do we evacuate the glass tube?
The better the vacuum, the better the electrons can travel unimpeded by collisions with gas molecules. A beam of electrons won't get far in air before being scattered.
 
  • #4
Uh, I see.. Great thanks.
 
  • #5


Evacuating the glass tube in the J.J. Thomson experiment is crucial for several reasons. Firstly, it removes any air molecules that may interfere with the path of the electrons being studied. This ensures that the electrons are not deflected or slowed down by collisions with air molecules, allowing for more accurate measurements of their behavior.

Secondly, the evacuated tube creates a low-pressure environment, which allows for the electrons to travel further without colliding with any particles. This increases the accuracy and precision of the measurements.

Lastly, the low-pressure environment also allows for the creation of a visible beam of electrons, which is necessary for the experiment to be observed and measured. Without the evacuation of the tube, the electrons would not be able to travel far enough to create a visible beam.

In summary, evacuating the glass tube in the J.J. Thomson experiment is essential for creating a controlled environment that allows for accurate measurements of the e/m ratio. It removes any interfering particles and creates a visible beam of electrons, making it a crucial step in the experiment.
 

1. What is the e/m ratio and why is it important?

The e/m ratio, also known as the charge-to-mass ratio, is a physical constant that represents the ratio of an electron's charge to its mass. It is important because it allows us to determine the mass of the electron, which is a fundamental particle in the structure of atoms and plays a crucial role in understanding the properties of matter.

2. Who is J.J. Thomson and what was his contribution to the discovery of the e/m ratio?

J.J. Thomson was a British physicist who is best known for his research on cathode rays and the discovery of the electron. In 1897, he conducted a series of experiments that led to the determination of the e/m ratio, which provided evidence for the existence of electrons and their charge-to-mass ratio.

3. How did Thomson's experiment work?

Thomson's experiment involved passing a beam of cathode rays through a magnetic field and measuring the deflection of the rays. He found that the degree of deflection was directly proportional to the strength of the magnetic field and inversely proportional to the velocity of the electrons. By manipulating the magnetic field and the voltage of the cathode ray tube, Thomson was able to calculate the e/m ratio.

4. What were the major implications of Thomson's discovery of the e/m ratio?

Thomson's discovery of the e/m ratio provided evidence for the existence of the electron and helped to establish the idea that atoms are composed of smaller, indivisible particles. This challenged the previously accepted theory of the indivisibility of atoms and paved the way for further discoveries in the field of atomic structure and particle physics.

5. How has the e/m ratio been refined and measured since Thomson's experiment?

Since Thomson's experiment, the e/m ratio has been measured and refined using various techniques, such as the Millikan oil drop experiment and modern methods like mass spectrometry. These methods have allowed for more accurate measurements of the electron's mass and charge, leading to a better understanding of the fundamental properties of matter.

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