Angle of incidence is defined as the angle at which a ray of light strikes a surface measured from the...

Angle of incidence is defined as the angle at which a ray of light strikes a surface measured from the...

• A. Normal
• B. Tangent
• C. Surface
• D. Axis

Answer: (A)

The angle of incidence is defined as the angle between the incoming ray and the normal to the surface at the point of contact. The normal is a line perpendicular to the surface, which provides a stable reference that stays consistent no matter how the surface is tilted. Measuring from the tangent would tie the angle to the surface itself and vary with its orientation, and measuring from an arbitrary axis isn’t tied to the surface geometry at all. This normal-based definition is also what makes the law of reflection work: the incident angle equals the reflected angle when both are measured from the normal. For a ray hitting a surface at 30 degrees to the normal, you’d see the same 30-degree relationship on the other side of the normal.

The angle of incidence is defined as the angle between the incoming ray and the normal to the surface at the point of contact. The normal is a line perpendicular to the surface, which provides a stable reference that stays consistent no matter how the surface is tilted. Measuring from the tangent would tie the angle to the surface itself and vary with its orientation, and measuring from an arbitrary axis isn’t tied to the surface geometry at all. This normal-based definition is also what makes the law of reflection work: the incident angle equals the reflected angle when both are measured from the normal. For a ray hitting a surface at 30 degrees to the normal, you’d see the same 30-degree relationship on the other side of the normal.