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Questions and Answers
What is the purpose of the electrodes in a cathode ray tube?
What can be adjusted in a cathode ray tube by evacuation?
What is the primary constituent of all atoms?
What does the charge-to-mass ratio of an electron depend on?
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When an electric field is applied to a cathode ray tube, what happens to the electrons?
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What is the effect of increasing the strength of the magnetic field on electron deflection?
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What is the purpose of balancing the electrical and magnetic field strengths in a cathode ray tube?
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What is the point where the electrons hit the screen when only a magnetic field is applied?
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What was the major limitation of Dalton's atomic theory?
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What was the significance of the discovery of subatomic particles?
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What was the main challenge faced by scientists after the discovery of subatomic particles?
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What was the significance of the experiments involving substances like glass or ebonite?
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What was the main contribution of John Dalton to the field of chemistry?
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What was the main limitation of Dalton's atomic theory in terms of its ability to explain experimental results?
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Study Notes
Discovery of Electron
- In 1830, Michael Faraday demonstrated that passing electricity through a solution of an electrolyte results in chemical reactions at the electrodes, suggesting the particulate nature of electricity.
- Faraday formulated laws that will be studied in class XII, which led to insights into the structure of atoms.
- Experiments on electrical discharge through gases, particularly in cathode ray discharge tubes, revealed the existence of electrons.
Cathode Ray Discharge Tube
- A cathode ray tube consists of a glass tube containing two thin pieces of metal (electrodes) sealed inside.
- When a high voltage is applied across the electrodes, a stream of particles (electrons) flows from the negative electrode (cathode) to the positive electrode (anode).
Charge to Mass Ratio of Electron
- In 1897, J.J. Thomson measured the ratio of electrical charge (e) to the mass of an electron (me) using a cathode ray tube and applying electrical and magnetic fields.
- Thomson found that the deflection of electrons depends on the magnitude of the negative charge, mass of the particle, and strength of the electrical or magnetic field.
Atomic Theory of Matter
- John Dalton proposed the atomic theory of matter in 1808, regarding the atom as the ultimate particle of matter.
- However, Dalton's theory did not account for the existence of subatomic particles, which were later discovered through experiments in the late 19th and early 20th centuries.
- The discovery of subatomic particles like electrons, protons, and neutrons led to a new understanding of the structure of atoms.
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Description
Learn about the discovery of electrons and protons, and their role in the structure of atoms. Explore the experiments and laws that led to our understanding of these particles.
