Two flat rectangular mirrors are set edge to edge and placed perpendicular to a flat nonreflecting surface. The edges of the two mirrors meet at a 30° angle. A light ray that approaches mirror 1 is parallel to mirror 2. The angle of reflection of that ray from mirror 1 is:

Angle of refelction is 60°

Explanation:

Let two mirrors XY and ZY meet at Y such that ∠XYZ = 30°

Let an incident ray PO incident on the 1st mirror XY and is parallel to the 2nd mirror YZ.

Let ON be the normal.

Now we know that, angle of incidence is equal to the angle of reflection

∴∠PON = ∠NOQ = 60°

Therefore, the angle of reflection of the ray incident on the 1st mirror is 60 degree.