KS5 Optics

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Wave Properties & Optics - Objectives


• Refraction of light

• Total internal reflection

• Interference

• Diffraction

• Two-source interference

Learning Outcomes

Students should know about:

  • Refractive index of a substance s , ns = c/cs; Candidates are not expected to recall methods for determining refractive indices
  • The refractive index of air being approximately 1
  • Snell's Law of refraction for a boundary between two different substances of refractive indices n1 and n2 in the form:
    n1sin θ1 = n2sin θ2
  • Total internal reflection including calculations of the critical angle θc at a boundary between a substance of refractive index n1 and a substance of lesser refractive index n2 or air:
    sin θc = n2/ n1
  • Simple treatment of fibre optics including function of the cladding with lower refractive index around central core limited to step index only; application to communications.
  • Material and modal dispersion
  • the principles and consequences of pulse broadening and absorption
  • Appearance of the diffraction pattern from a single slit using monochomatic and white light
  • the qualitative treatment of the variation of the width of the central diffraction maximum with the wavelength and slit width (intesity-angular separation graph is not required)
  • The plane transmission diffraction grating at normal incidence; optical details of the spectrometer will not be required
  • Derivation of d sin θ = nλ, where n is the order number
  • Applications; e.g. to spectral analysis of light from stars
  • The concept of path difference and coherence
  • The laser as a source of coherent monochromatic light used to demonstrate interference and diffraction; comparison with non-laser light; awareness of safety issues. Candidates will not be required to describe how a laser works.
  • Young's double-slit experiment: the use of two coherent sources or the use of a single source with double slits to produce an interference pattern
  • The appearance of the interference fringes produced by a double slit system, fringe spacing, w = λD/s , where s is the slit separation.
  • the production of an interference pattern using white light
  • how to describe and explain interference produced with sound and electromagnetic waves
  • how the understanding of the nature of electromagnetic radiation has changed over time
  • REQUIRED PRACTICAL - investigation of interference effects to include the Young's double-slit experiment and interference by a diffraction grating

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