Matter and Materials

Optical phenomena and properties of materials
Transmission and scattering of light

• Explain the interaction of UV and visible radiation:
  · with metals: (reflect and re-emit)
  · in terms of the interaction with electromagnetic radiation
• Explain why the sky is blue

Photoelectric effect

• Describe the photoelectric effect as the process that occurs when light shines on a metal and it ejects an electron
• Explain the photoelectric effect in terms of photons and work function.
• Recall, use and explain the significance of :
  
  where W₀ is the work function of a surface
• Give the significance of the photo-electric effect:
  · it establishes the quantum theory
  · it illustrates the particle nature of light

Emission and absorption spectra

• Explain the source of atomic emission spectra (cf discharge tubes) and their unique relationship to each element
• Relate the lines on the atomic spectrum to electron transitions between energy levels
• Explain the difference between atomic absorption and emission spectra
• Use E = hf to determine the energy of photons of UV and visible light of varying colours
• Relate UV and visible light to atomic absorption spectra

Lasers

• Explain and contrast the concepts of spontaneous emission of radiation and stimulated emission of radiation
• State that lasers emit light which is monochromatic and in phase
• Explain, in simple terms, how a laser works.
  · Include concepts of:
  · a metastable state,
  · population inversion
  · and the consequence of the decay of some atoms from the meta-stable state,
  · and their subsequent stimulation of other excited atoms to emit photons in phase with this emission.
• Recognise that the materials used for lasers all allow a population inversion to be set up and that materials which have been used include:
  · synthetic ruby
  · a mixture of helium and Neon (He-Ne lasers)
  · and various semi-conductors
• Describe the arrangement of the laser cavity and its effects of:
  · increasing amplification
  · concentrating beam intensity
  · improving the spectral purity of the beam (narrowing the frequency of the beam)
• Identify some advantages of laser applications in respect of:
  · barcodes
  · laser communication and fibre optics
  · medical lasers
  · laser printers
  · optical storage media