Which pair of optical angles is defined as being measured from the normal?

Which pair of optical angles is defined as being measured from the normal?

• A. Angle of incidence and angle of refraction
• B. Angle of incidence and angle of reflection
• C. Angle of reflection and angle of dispersion
• D. Angle of incidence and angle of rotation

Answer: (B)

In optics, angles are measured relative to the normal, the line perpendicular to the surface where the ray strikes. The angle of incidence is the angle between the incoming ray and this normal, and the angle of reflection is the angle between the reflected ray and the normal. Because both angles use the same reference line, they are defined from the normal, making them a natural pair for reflection at a boundary (and the law of reflection states they are equal). The other terms refer to ideas not defined by a reference to the normal (dispersion relates to wavelength dependence; rotation is not a standard optical angle). So the pair defined from the normal is the angle of incidence and the angle of reflection.

In optics, angles are measured relative to the normal, the line perpendicular to the surface where the ray strikes. The angle of incidence is the angle between the incoming ray and this normal, and the angle of reflection is the angle between the reflected ray and the normal. Because both angles use the same reference line, they are defined from the normal, making them a natural pair for reflection at a boundary (and the law of reflection states they are equal). The other terms refer to ideas not defined by a reference to the normal (dispersion relates to wavelength dependence; rotation is not a standard optical angle). So the pair defined from the normal is the angle of incidence and the angle of reflection.