The ______ of a ray is the angle measured from the reflected ray to the normal surface.

The correct answer is Angle of Reflection.

Key Points

Reflection-

• When the light rays fall on the plane surface and deviate from their path in the same medium or when a ray of light incident on the plane surface is reflected back into the same medium it is termed as Reflection.
  • Example - Plane Mirror.

Laws of Refraction:

• The incident ray, the refracted ray, and the normal interface of two transparent media at the point of incidence, all lie in the same plane.
• The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for the light of a given color and for the given pair of media.
• This law is also known as Snell’s law of refraction.

Explanation:

• When a ray of light is incident normally on the surface it retraces its path after reflection.

Angle of incidence = Angle of reflection = 90°

So, when the light ray is an incident normal to a surface then the reflected ray will be perpendicular to the surface

Additional Information 

• For refraction- 
  • The Normal, Incident ray and Refracted ray lie on the same plane at the point of Incidence.   
• For reflection- 
  • The Normal, Incident ray, reflected ray lie on the same plane at the point of Incidence