Question

what is the reason for the rectilinear propagation of light?

Answer 1

Do you remember being in school, and when the teacher projected something onto a screen some kids would love to make shadow animals with their hands? They would contort their hands to make a giraffe shadow or cat shadow or whatever animal they knew how to make. This experience actually tells us something: It tells us that light travels in straight lines, which is the meaning of rectilinear propagation. It's actually a unique phenomenon. Let's investigate further to understand why.

Answer 2

......................