Question

The first law of reflection requires that:

Options

• The reflected ray always lies perpendicular to the incident ray

• The incident ray and reflected ray lie in perpendicular planes

• The incident ray, reflected ray, and the surface tangent all lie in the same plane

• The incident ray, reflected ray, and the normal at the point of incidence all lie in the same plane

Answer 1

The first law of reflection is a coplanarity condition: the incident ray, the reflected ray, and the normal drawn at the point of incidence must all lie in one single plane. Only then is the angle relation between them defined.