State what is meant by polarisation and explain how it is used to distinguish between transverse and longitudinal waves.
An unpolarised light source passes horizontally through a fixed polarising filter A. An observer views the light emerging through a second polarising filter B, which may be rotated about point XY as shown in Figure 1.
Figure 1
The observer rotates B slowly through 360° clockwise.
Relative to polarising filter A, at which angles of polarising filter B does the observer see the maxima and minima amount of daylight.
On Figure 2 below, sketch how the light intensity reaching the observer varies as polarising filter B is rotated slowly through 360°.
Figure 2
Explain why when the transmission axis of polarising filter B is perpendicular to the plane XY, the observer does not see horizontally polarised light.
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