1. The problem statement, all variables and given/known data Can you explain why the for Y , the direction of reflection is in and out of page ? p/s : the wording is in the photo. so i think it's needless to retype it again . 2. Relevant equations 3. The attempt at a solution is it because for reflected ray, the ray will oscillate in and out of the page just as the reason (in your explaination above) ? for Z , the light ray is not reflected because of the incident light only vibrate up and down to the plane of incident , so the light ray which oscillate in and out of the page doesn't exist at all , so the light is unreflected?