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Polarisation and diffractionEdexcel International A Level Physics: Flashcards

What these 13 flashcards ask

  • What is plane-polarised light?
  • What is unpolarised light?
  • Which type of wave can be plane polarised?
  • Why can sound not be polarised?
  • What does polarisation provide evidence for?
  • What does a polarising filter do?
  • What do you see when two polarising filters are crossed (axes at 90°)?
  • How many times does the intensity fall to zero when a second filter is rotated through 360°?
  • What is diffraction?
  • When is diffraction most noticeable?
  • Which wave quantities are unchanged by diffraction?
  • State Huygens' construction.
  • How does Huygens' construction explain spreading at the edge of a gap?

Exam questions on Polarisation and diffraction

  1. A student shines light from a lamp through a sheet of polarising filter and then through a second sheet of the same material placed directly behind it. She looks at the light that emerges from the second sheet while rotating that sheet slowly in its own plane.
    Explain why the light emerging from the first sheet is plane polarised.2 marks
  2. A student shakes the free end of a long rope randomly in all directions in the plane at right angles to the rope. The rope passes through a narrow vertical slot cut in a wooden board and then, further along, through a second board with a narrow slot that can be turned to any orientation.
    The student repeats the demonstration with a long spring, pushing and pulling its end along the spring. Explain why a pair of slots has no effect on this wave however they are oriented.2 marks
  3. In a ripple tank, straight water waves of wavelength 3.0 cm travel at 0.12 m s⁻¹ towards a barrier. The barrier has a gap whose width can be adjusted by moving two metal bars.
    Describe how the waves behave after the barrier when the gap is 3.0 cm wide and when it is 30 cm wide.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).