Physics

The key here is understanding the law of reflection: the angle of incidence always equals the angle of reflection, both measured from the normal (the perpendicular to the mirror surface). Since you're given the angle with respect to the normal directly, you can immediately apply this law—the reflected ray will make the same $0.40\,\text{rad}$ angle on the opposite side of the normal. The challenge is often visualizing the geometry correctly and identifying what the problem is actually asking for (the reflected angle, the deviation of the ray, or the angle between incident and reflected rays).

The key here is understanding the law of reflection: the angle of incidence always equals the angle of reflection, both measured from the normal (the perpendicular to the mirror surface). Since you're given the angle with respect to the normal directly, you can immediately apply this law—the reflected ray will make the same $0.40\,\text{rad}$ angle on the opposite side of the normal. The challenge is often visualizing the geometry correctly and identifying what the problem is actually asking for (the reflected angle, the deviation of the ray, or the angle between incident and reflected rays).