The normal line is a line at a right angle (90 degrees) to the surface of an object

To draw a normal line to the mirror, you must draw a line at 90 degrees to the surface of the mirror.

Law of reflection - Reflection and refraction of light - CCEA - GCSE Physics (Single Science) Revision - CCEA - BBC Bitesize

What is flux in physics?

Normal line - Tilted flat mirrors

Angle of Incidence - Definition, Formula, Diagram, Examples

Azimuth - Wikipedia

Theorem - The tangent at any point of a circle is perpendicular to the radius through the point of contact - Circles

Physics Tutorial: Total Internal Reflection

Angle of Reflection Definition, Types & Formula - Lesson

Normal line - Tilted flat mirrors

Normal Line, Definition & Equation - Lesson