<P> In geometric optics , the angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence , called the normal . The ray can be formed by any wave : optical , acoustic , microwave , X-ray and so on . In the figure below , the line representing a ray makes an angle θ with the normal ( dotted line ) . The angle of incidence at which light is first totally internally reflected is known as the critical angle . The angle of reflection and angle of refraction are other angles related to beams . </P>
<P> In geometric optics , the angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence , called the normal . The ray can be formed by any wave : optical , acoustic , microwave , X-ray and so on . In the figure below , the line representing a ray makes an angle θ with the normal ( dotted line ) . The angle of incidence at which light is first totally internally reflected is known as the critical angle . The angle of reflection and angle of refraction are other angles related to beams . </P>
where is the angle of incidence measured from
where is the angle of incidence measured from
between a ray incident on a surface and the line perpendicular to the surface at the point of incidence , called the normal
between a ray incident on a surface and the line perpendicular to the surface at the point of incidence , called the normal