angle of incidence
Technical term in physics and optics; the angle between an incoming ray and the normal to a surface.
As the angle of incidence increases, the reflectance also changes.
Please measure the angle of incidence of the light.
Angle of refraction; the angle between the refracted ray and the normal when light passes into a different medium.
Compound of 入射 (にゅうしゃ, 'incidence') and 角 (かく, 'angle'). The term is a direct calque from English 'angle of incidence'.