Normal (Line) - GCSE Physics Definition

In GCSE Physics, a 'normal line' is an imaginary line that's drawn at a right angle (90 degrees) to a surface where something like a light ray hits it. By using this line, we can easily measure the angles of incidence (the angle in which the light hits the surface) and reflection (the angle in which the light bounces off the surface). The angles are measured to the normal line, and they help us predict and explain how waves behave when they meet different surfaces, such as a mirror.