According to the principle of reflection, when an incident light wave strikes a reflective surface at an angle of 30 degrees, at what angle will it reflect off the surface?

60°

Explanation:

According to principle of reflection, the angle of reflection is equal to the angle of incidence. The angle of incidence is the angle with the normal to the plane of incidence.

Here, the incident wave strikes the surface at 30° (that is from the horizontal).

Angle of incidence = 90° - 30° = 60°

Therefore, angle of reflection = 60°