Polarisation and diffractionEdexcel International A Level Physics: Mind map

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