Cathode Rays

Increased understandings of cathode rays led to the development of television

Students learn to:

• explain why the apparent inconsistent behaviour of cathode rays caused debate as to whether they were charged particles or electromagnetic waves
• explain that cathode ray tubes allowed the manipulation of a stream of charged particles
• identify that moving charged particles in a magnetic field experience a force
• identify that charged plates produce an electric field
• describe quantitatively the force acting on a charge moving through a magnetic field 
• discuss qualitatively the electric field strength due to a point charge, positive and negative charges and oppositely charged parallel plates
• describe quantitatively the electric field due to oppositely charged parallel plates
• outline Thomson’s experiment to measure the charge/mass ratio of an electron
• outline the role of:
  • electrodes in the electron gun
  • the deflection plates or coils the fluorescent screen

  in the cathode ray tube of conventional TV displays and oscilloscopes

Students:

• perform an investigation and gather first-hand information to observe the occurrence of different striation patterns for different pressures in discharge tubes
• perform an investigation to demonstrate and identify properties of cathode rays using discharge tubes:
  • containing a maltese cross
  • containing electric plates
  • with a fluorescent display screen
  • containing a glass wheel
  • analyse the information gathered to determine the sign of the charge on cathode rays
• solve problems and analyse information using: