[Physics Form 5] Cathode Rays

Question:
How are cathode rays formed?

Answer:

• The 6V source first heats up the filament, which, in turn, heats up the cathode.
  
  
• The cathode thus exhibits thermionic emission and produces thermal electrons.
  
  
• The EHT exerts a strong electric field between the cathode and the anode, causing the thermal electrons to accelerate, and travel at a high speed and in a straight line towards the anode.
  
  
• The beam of fast-moving electrons generated is known as cathode rays.