1. Light travels in straight lines in a homogeneous and isotropic medium.
2.When light reflects off a smooth surface, the angle of incidence is equal to the angle of reflection. The incident ray, reflected ray, and the normal to the surface at the point of incidence lie in the same plane.
3.When light passes from one medium to another, it bends according to Snell's Law:
where n1 and n2 are the refractive indices of the two media, and θ1 and θ2 are the angles of incidence and refraction, respectively.
4. The path of a light ray is reversible. If a ray of light follows a path from point A to point , it will follow the same path in reverse when traveling from to .
5.Light rays do not interact with each other when they cross. The intensity at a point is the algebraic sum of the intensities of individual rays.
6.Light travels between two points along the path that requires the least time, which may be a straight or curved path depending on the medium.