⁄2 max Energy of a charged particle in an electric field
Energy conversion of a charged particle in an electric field Energy of a photon
Einstein’s photoelectric equation Work function
CONCEPTS: ■ The electron: charge, mass and location ■ Units of energy: eV, keV, MeV, GeV ■ Thermionic emission: basic principle and application ■ Cathode ray tube: heated filament, cathode, anode and screen ■ Deflection of cathode rays in electric and magnetic fields ■ X-rays: production (inverse of photoelectric effect) and properties (ionisation and penetration) ■ Photoelectric emission: basic principle and application, effect of intensity and frequency of incident light ■ The photon: a packet of energy ■ Einstein’s photoelectric law ■ Threshold frequency ■ Photocell (vacuum tube): structure and operation
ACTIVITIES:
■ Use of cathode ray tube to demonstrate the production of a beam of electrons: deflection in electric and magnetic fields
■ Demonstration of photoelectric effect (using zinc plate, electroscope and different light sources) ■ Demonstration of a photocell
SCIENCE,TECHNOLOGY AND SOCIETY: ■ Electron named by G.J. Stoney ■ Quantity of charge measured by Millikan ■ Applications of cathode ray tubes: television, cathode ray oscilloscope (ECG and EEG) ■ Uses of X-rays in medicine and industry and the hazards associated with them
■ Applications of photoelectric sensing devices: burglar alarms, automatic doors, control of burners in central heating, soundtrack in films
PHYSICAL QUANTITIES INTRODUCED IN THIS CHAPTER: Quantity
