Percobaan Sinar Katoda oleh J.J Thomson

Introduction

This tutorial provides a comprehensive guide on the cathode ray experiment conducted by J.J. Thomson, a pivotal moment in physics that led to the discovery of the electron. Understanding this experiment is essential for grasping the fundamentals of atomic structure and the development of modern physics.

Step 1: Setting Up the Apparatus

To replicate the cathode ray experiment, you will need specific components. Ensure you have the following:

• A cathode ray tube (CRT)
• A high voltage power supply
• A vacuum pump (to create a low-pressure environment)
• A phosphorescent screen
• Electrodes (anode and cathode)

Instructions for Setup

1. Assemble the Cathode Ray Tube: Ensure the tube is sealed and able to maintain a vacuum.
2. Connect the Electrodes: Attach the cathode and anode to the high voltage power supply.
3. Create a Vacuum: Use the vacuum pump to remove air from the tube, allowing the electrons to move freely.
4. Prepare the Screen: Position the phosphorescent screen at the end of the tube to visualize the cathode rays.

Step 2: Conducting the Experiment

Once your apparatus is set up, you can begin the experiment.

Procedure

1. Power On the Supply: Switch on the high voltage power supply to create a potential difference between the electrodes.
2. Observe the Cathode Rays: As the electrons are emitted from the cathode, they will travel towards the anode and strike the phosphorescent screen, producing a visible glow.
3. Adjusting the Setup: Experiment with different angles and distances of the screen to observe changes in the brightness and direction of the rays.

Step 3: Analyzing Results

After you have conducted the experiment, analyze your observations.

Key Points for Analysis

• Direction of Rays: Note that the rays travel in straight lines from the cathode to the anode.
• Effect of Magnetic Fields: Introduce a magnetic field to see how it alters the path of the rays, confirming their charged nature.
• Measure Deflection: Use a scale to measure how far the rays deflect in the presence of the magnetic field, which can give insights into the charge-to-mass ratio of the particles.

Step 4: Understanding the Implications

Reflect on the implications of the experiment.

Discussion Points

• Discovery of Electrons: Thomson's experiment led to the conclusion that cathode rays are composed of negatively charged particles, later named electrons.
• Model of the Atom: This experiment shifted the understanding of atomic structure, leading to the development of the "plum pudding model."
• Impact on Future Research: Consider how this laid the groundwork for future discoveries in atomic physics and quantum mechanics.

Conclusion

J.J. Thomson's cathode ray experiment is a foundational experiment that revolutionized our understanding of atomic structure. By following the steps outlined in this tutorial, you can replicate the experiment and grasp the key concepts behind the discovery of electrons. As a next step, consider exploring more advanced topics in atomic theory or conducting further experiments related to particle physics.