Abstract
According to Fermat's principle, a ray of light travelling between two points traverses a path such that the time taken is a stationary value. However, in many textbooks the principle is often stated less rigorously by saying that a light ray follows the path of least time. Examples in which a ray traverses a path requiring a non-minimum time are, however, not uncommon for both reflection and refraction at spherical/cylindrical surfaces. Kaushik and Sukheeja (1984) gave an example of a path of maximum time in reflection while Halliday and Resnick (1966) gave an example of a path of maximum time in refraction when the angle of incidence is zero. The author first discusses the general condition for obtaining stationary optical paths in reflection by a spherical surface; then he considers the similar situation in refraction.
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