The Electron

The Electron

1. Subatomic particles

   • Protons
     • Mass = 1 u
     • Charge = +1
   • Neutrons
     • Mass = 1 u
     • Charge = 0
   • Electrons
     • Charge = -1
     • Mass = 1/1840 u
   • Unified atomic mass unit
     • Unit of mass used to express atomic and molecular masses
     • Symbol = u
     • 1.66 x 10*-27 kg

2. Energy of an electron

   • E = qV
     • E = energy
     • q = charge
     • V = voltage
   • Measured in electronvolts
     • 1 eV = 1.6 x 10*-19
   • Energy conversion of a charged particle in an electric field
     • Potential to kinetic or vice versa
     • qV = 1/2 mv*2

3. Thermionic Emission

   • The emission of electrons from the surface of a hot metal
   • Work function
     • Minimum energy needed to remove the loosest electrons from the surface of a metal
   • Occurs over 800 degrees C

4. Cathode Ray Tube

   • Components
     • A vacuum inside a glass tube
     • A hot filament
     • An anode & a cathode
     • A fluorescent screen
   • Thermionic emission occurs at the cathode
   • Properties of cathode rays
     • Travel in straight lines
     • Cause zinc sulphide to give out light when they strike it
     • They have kinetic energy
     • Deflected in electric or magnetic fields
     • Produce X-Rays

5. X-rays

   • Electromagnetic radiation of very high frequency
   • Properties
     • Electromagnetic waves
     • Penetration
     • Ionisation

6. Photoelectric effect

   • Emision of electrons from the surface of a metal due to electromagnetic radiation of a suitable frequency hitting the metal
   • Photon
     • Bundle of light energy
     • E = hf
       • E = energy
       • h = Planck's constant
       • f = frequency