At what angle of incidence do the incident and reflected rays of light make a right angle?

The angle of incidence ∠α is the angle between the incident ray and the perpendicular to the plane that reflects, drawn to the point of incidence of the ray.
The angle of reflection ∠β is the angle between the reflected ray and the perpendicular to the plane that reflects, drawn to the point of incidence of the ray.
The angle of incidence ∠α is equal to the angle of reflection ∠β.
∠α = ∠β.
A right angle has a degree measure of 90 degrees.
By hypothesis, ∠α + ∠β = 90.
∠α = ∠β = 90/2 = 45.
Answer: At an angle of incidence of 45 degrees, the incident and reflected rays of light make up a right angle.