- The field of geometric optics uses the idea that light is made up of rays when describing and explaining what happens when it encounters different media.
- Light rays are not real, they are a concept used to produce an idealised explanation of light.
- Ray diagrams use straight lines and arrows to show how light propagates.
- In the natural world light is not really made up of rays. More accurate descriptions of the properties of light use terms such as photons or waves.
- So a light ray is a diagrammatic representation of a narrow beam of light travelling through a vacuum or medium.
- The nearest thing to a light ray in the real world is a narrow focused beam of light produced by a laser.
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