(a) List two properties of cathode rays (b) Explain how the intensity and energy of cathode rays may be increased

Answer Details

(a) Two properties of cathode rays:

• They travel in straight lines and cast sharp shadows of objects placed in their path.
• They are negatively charged, so they are deflected by both electric and magnetic fields.
• They possess kinetic energy (produce heat) and cause certain substances to fluoresce; they travel from cathode to anode.

(b) Increasing the intensity and energy of cathode rays:

• Intensity (the number of electrons emitted per second) is increased by raising the temperature of the cathode, i.e. increasing the heating (filament) current, so that more electrons are emitted by thermionic emission.
• Energy (the speed/kinetic energy of the electrons) is increased by raising the accelerating potential difference between the cathode and the anode, since each electron gains kinetic energy \( \tfrac{1}{2}mv^2 = eV\).