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Asked in GSEB Board July 2022 · Malus's law and polaroids
Given: four ways of drawing a ray of light, and we want the one showing light polarised in the plane of the paper.
Idea: in these diagrams the electric field's vibration is drawn wherever it can be drawn -- a double-headed arrow across the ray for a vibration lying in the plane of the paper, a dot on the ray for a vibration perpendicular to that plane (seen end-on), and both together for unpolarised light.
Panel (2) carries only double-headed arrows drawn across the ray, and an arrow across the ray lies in the plane of the paper.
So the vibration there is confined to a single direction within the plane of the paper: plane polarised light, polarised in the plane of the paper.
For contrast, panel (1) is light polarised at right angles to the paper, panel (3) is unpolarised light, and panel (4) shows a longitudinal vibration, which light cannot have.
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