Critical Angle

The critical angle is specific to each pair of media. For glass with a refractive index of 1.5, the critical angle is approximately 42$^\circ$.

At the critical angle, the refracted ray travels along the boundary between the two media. Above the critical angle, no refraction occurs and all the light is reflected back into the denser medium (total internal reflection).

$n = \frac{1}{\sin c}$

This relationship links the refractive index of the denser medium to its critical angle.