Intensity and polarisationEdexcel A-Level Physics: Mind map

Exam questions on Intensity and polarisation

1. A small lamp in a large dark hall behaves as a point source. It radiates 12 W of light uniformly in all directions, and none of the light is absorbed by the air.
   State what is meant by the intensity of a wave and explain why the intensity of the light falls as the distance from the lamp increases.2 marks
2. An engineer tests solar panels outdoors. At midday the intensity of sunlight, measured perpendicular to the surface of the panels, is 1000 W m⁻². The first panel has an area of 1.6 m² and an efficiency of 18%, meaning that 18% of the incident power is converted to electrical power.
   A second panel has an efficiency of 15% and must also deliver 288 W in the same sunlight. Calculate the area it needs.2 marks
3. A fisherman wears polarising sunglasses. Light reflected from the surface of a calm lake is partially plane polarised with its oscillations mainly horizontal. The lenses of the sunglasses have a vertical transmission axis.
   Explain what is meant by plane polarisation and why sound waves cannot be plane polarised.3 marks