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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
A cathode ray is produced when a high-voltage power supply is connected to the discharge tube, energizing the cathode. This causes electrons to be emitted from the cathode. These emitted electrons are then accelerated towards the anode, resulting in a stream of charged particles known as a cathode ray.
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
To restore the cathode ray to its original path, the electric field strength between plates P and Q must be adjusted. Increasing the electric field strength produces a stronger force on the charged particles, counteracting any deflection caused by the charged 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 can also restore the cathode ray's path. By increasing the magnetic flux density, the magnetic force acting on the moving charged particles becomes stronger, which can counterbalance the effects of their increased speed and keep them on their original trajectory.
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 were significant as they showed that the specific charge of cathode rays (which are electrons) is much greater than the specific charge of the hydrogen ion. This indicates that electrons carry a smaller mass relative to their charge when compared to ions. The implications are profound in understanding the nature of atoms and the subatomic structure, as it established that cathode rays (electrons) are fundamental particles with properties distinct from those of ions.