24.3: Lenses - Physics LibreTexts
https://phys.libretexts.org/Bookshelves/University_Physics/Physics_(Boundless)/24%3A_Geometric_Optics/24.3%3A_Lenses
WEBRay tracing is the technique of determining or following (tracing) the paths that light rays take. Experiments, as well as our own experiences, show that when light interacts with objects several times as large as its wavelength, it travels in straight lines and acts like a ray. (A ray is simply a straight line that originates at a point.
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