Which phenomenon is evidence of the rectilinear propagation of light?

The straightforwardness of the propagation of light in a homogeneous medium explains the formation of a shadow. Shadows of people, trees, buildings and other objects are well observed on the ground on a sunny day.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.