Chat with our AI personalities
It's the extension of the sphere's radius drawn to that point.
The normal vector to the surface is a radius at the point of interest.
That ray of light is just a radius of the sphere. It's perpendicular to the sphere everywhere, so the angle of incidence is zero ... the ray of light arrives along the normal to the mirror at any point.
The radius of a sphere is equal distance from the center of the sphere to all points within the sphere.
Sphere is one syllable: sphere.