Ch.2 - Atoms, Molecules & Ions

Problem 87

Chapter 2, Problem 87

What affects the magnitude of the deflection of the cathode ray in Thomson's experiment?

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Understand that the cathode ray in Thomson's experiment is composed of electrons, which are negatively charged particles.

Recognize that the deflection of the cathode ray is influenced by the electric and magnetic fields applied in the experiment.

Identify that the magnitude of the deflection is directly proportional to the charge of the particles and inversely proportional to their mass, as described by the equation: \( F = q(E + v \times B) \), where \( F \) is the force, \( q \) is the charge, \( E \) is the electric field, \( v \) is the velocity, and \( B \) is the magnetic field.

Consider that increasing the strength of the electric or magnetic field will increase the deflection of the cathode ray.

Acknowledge that the velocity of the electrons also affects the deflection; higher velocities result in less deflection due to the inertia of the particles.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cathode Rays

Cathode rays are streams of electrons observed in vacuum tubes. They are produced when electrons are emitted from a cathode and travel towards an anode. The behavior of cathode rays, including their deflection, is crucial for understanding the nature of electric charge and the structure of atoms, as demonstrated in Thomson's experiment.

Electric and Magnetic Fields

The deflection of cathode rays in Thomson's experiment is influenced by external electric and magnetic fields. When these fields are applied, they exert forces on the charged particles (electrons), causing them to change direction. The strength and orientation of these fields directly affect the degree of deflection observed.

Charge-to-Mass Ratio

The charge-to-mass ratio of the electrons is a critical factor in determining how much they will deflect in an electric or magnetic field. A higher charge-to-mass ratio results in greater deflection for a given field strength. Thomson's experiment aimed to measure this ratio, providing insights into the properties of electrons and their role in atomic structure.

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Textbook Question

Two compounds containing carbon and oxygen have the following percent composition by mass. Compound 1: 42.9% carbon and 57.1% oxygen Compound 2: 27.3% carbon and 72.7% oxygen Show that the law of multiple proportions is followed. If the formula of the first compound is CO, what is the formula of the second compound?

Label the following statements about J. J. Thomson's cathode-ray tube experiments shown in Figure 2.6 as true or false. (b) A cathode ray is a stream of charged particles.

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Textbook Question

Label the following statements about J. J. Thomson's cathode-ray tube experiments shown in Figure 2.6 as true or false. (c) The cathode ray is deflected away from a positively charged plate.

Label the following statements about J. J. Thomson's cathode-ray tube experiments shown in Figure 2.6 as true or false. (f) By measuring the deflection of the cathode ray beam caused by electric fields of known strength, the charge-to-mass ratio of the electron was calculated.

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