Ideas to implementation - 9.4.1

9.4.2The re-conceptualisation of the model of light led to an understanding of the photoelectric effect and black body radiation
  • describe Hertz’s observation of the effect of a radio wave on a receiver and the photoelectric effect he produced but failed to investigate
  • outline qualitatively Hertz’s experiments in measuring the speed of radio waves and how they relate to light waves
  • identify Planck’s hypothesis that radiation emitted and absorbed by the walls of a black body cavity is quantised
  • identify Einstein’s contribution to quantum theory and its relation to black body radiation
  • explain the particle model of light in terms of photons with particular energy and frequency
  • identify the relationships between photon energy, frequency, speed of light and wavelength: E=hf c=f λ
  • identify that some electrons in solids are shared between atoms and move freely
  • describe the difference between conductors, insulators and semiconductors in terms of band structures and relative electrical resistance
  • identify absences of electrons in a nearly full band as holes, and recognise that both electrons and holes help to carry current
  • qualitatively the relative number of free electrons that can drift from atom to atom in conductors, semiconductors and insulators
  • identify that the use of germanium in early transistors is related to lack of ability to produce other materials of suitable purity
  • - describe how ‘doping’ a semiconductor can change its electrical properties
  • identify differences in p and n-type semiconductors in terms of the relative number of negative charge carriers and positive holes
  • describe differences between solid state and thermionic devices and discuss why solid state devices replaced thermionic devices
9.4.4 Investigations into the electrical properties of particular metals at different temperatures led to the identification of superconductivity and the exploration of possible applications
  • outline the methods used by the Braggs to determine crystal structure
  • - identify that metals possess a crystal lattice structure
  • describe conduction in metals as a free movement of electrons unimpeded by the lattice
  • identify that resistance in metals is increased by the presence of impurities and scattering of electrons by lattice vibrations
  • describe the occurrence in superconductors below their critical temperature of a population of electron pairs unaffected by electrical resistance
  • discuss the BCS theory
  • - discuss the advantages of using superconductors and identify limitations to their use
  • process information to identify some of the metals, metal alloys and compounds that have been identified as exhibiting the property of superconductivity and their critical temperatures
  • perform an investigation to demonstrate magnetic levitation
  • analyse information to explain why a magnet is able to hover above a superconducting material that has reached the temperature at which it is superconducting
  • gather and process information to describe how superconductors and the effects of magnetic fields have been applied to develop a maglev train
  • process information to discuss possible applications of superconductivity and the effects of those applications on computers, generators and motors and transmission of electricity through power grids