Question

For a curved surface such as a spherical mirror, the normal used in applying the laws of reflection is taken as:

Options

• The normal to the principal axis at the pole

• A line parallel to the principal axis through the point of incidence

• The line joining the point of incidence to the pole

• The normal to the tangent to the surface at the point of incidence

Answer 1

For a curved surface such as a spherical mirror, the normal is taken as the normal to the tangent to the surface at the point of incidence. Since this normal is perpendicular to the tangent, it lies along the radius through that point.