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Figure 1 shows a diagram of a discharge tube used by JJ Thomson to investigate cathode rays - AQA - A-Level Physics - Question 1 - 2020 - Paper 7
Question 1
Figure 1 shows a diagram of a discharge tube used by JJ Thomson to investigate cathode rays. The direction XY is horizontal and at right angles to the axis of the t... show full transcript
Worked Solution & Example Answer:Figure 1 shows a diagram of a discharge tube used by JJ Thomson to investigate cathode rays - AQA - A-Level Physics - Question 1 - 2020 - Paper 7
Step 1
Describe how a cathode ray is produced in the discharge tube in Figure 1.
Answer
In the discharge tube, when a high-voltage power supply is connected, it creates a potential difference that accelerates electrons from the cathode. These electrons then move towards the anode and form a cathode ray as they are emitted into the vacuum of the tube. The cathode ray can be observed as it strikes the fluorescent screen, causing it to glow.
Step 2
Step 3
Explain how the cathode ray is restored to its original path by adjusting only the electric field strength between P and Q.
Answer
By increasing the electric field strength between plates P and Q, the force acting on the charged particles can be adjusted. This ensures that the particles are deflected back along their original path, countering the deflection caused by the plates.
Step 4
Explain how the cathode ray is restored to its original path by adjusting only the magnetic flux density.
Answer
Adjusting the magnetic flux density modifies the magnetic force acting on the charged particles. By increasing or decreasing this flux density, it can effectively counteract the deflection of the particles, allowing them to travel back along their original path.
Step 5
Discuss the significance of Thomson’s results for the particles in cathode rays, when compared with the specific charge of the hydrogen ion.
Answer
Thomson’s results demonstrated that the specific charge of particles in cathode rays was significantly greater than that of hydrogen ions. This finding indicated that electrons had a much larger charge-to-mass ratio than hydrogen ions, which contributed to the understanding that these particles were fundamental to atomic structure, challenging previous notions of atomic particles and leading to the development of modern atomic theory.