Question

What is the ratio between angle of incidence to the angle of reflection in case of
regular reflection​

Answer 1

The ratio between angle of incidence and angle of reflection is always 1 : 1. Because the angle on incidence is always equal to the angle of reflection.

For example let the angle of incidence be "x" say

then, the angle of incidence is equal to angle of reflection.

so, x : x = 1 : 1.

Hope this helps you.