Light Path in Gravitational Field by Hayden\'s formula and Fermat\'s Principle
Keywords: light path, gravitational field, Hayden's formula, Fermat's principle, Einstein's General Theory
The optical part of the trajectory of light in a gravitational field is derived from Hayden\'s expression for the refractive index and Fermat\'s principle. The bending angle obtainable from it agrees with Hayden\'s result. Unlike the approximate trajectory derived under the assumptions of Einstein\'s General Theory, the trajectory derived from Fermat\'s principle is an exact result in closed form.