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The Critical Angle and Total Internal Reflection. The Critical Angle and Total Internal Reflection can only occur if the second medium has an index of refraction less than the first medium. Critical Angle : the angle at which light is refracted at 90 º.
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The Critical Angle and Total Internal Reflection The Critical Angle and Total Internal Reflection can only occur if the second medium has an index of refraction less than the first medium. Critical Angle: the angle at which light is refracted at 90º. Total Internal Reflection: The reflection of light from the boundary of a medium with a smaller index of refraction into a medium with a greater index of refraction once the critical angle is exceeded.
Refraction When the incident angle (θ1) is less than the critical angle, then the light is refracted into the next medium – Snell’s Law applies. n1>n2 θ1 n1 Medium 1 n2 Medium 2 θ2
Critical Angle • When the angle of incidence (θ1) causes the light in the new medium to refract at 90º, then the angle of incidence is equal to θc. θ1 at θc n1>n2 θc 90º n1 n2 n1 sin θc=n2 sin 90º
Total Internal Reflection • Any incident angle greater than the critical angle causes total internal reflection. The light ray is no longer refracted, but reflected. The law of reflection applies. n1>n2 θ1=θ2 θ1 θ2 n1 n2
