cos_critical

iadpython.fresnel.cos_critical(n_i, n_t)

Calculate the cosine of the critical angle.

This works for arrays too. If there is no critical angle then cos(pi/2)=0 is returned.

\[\theta_c = \sin^{-1}(n_t / n_i)\]

The cosine of this angle is then

\[\cos(\theta_c) = \cos(\sin^{-1}(n_t / n_i))\]

\[\cos(\theta_c) = \sqrt{1-(n_t/n_i)^2}\]

Parameters:

• n_i – index of refraction of incident medium

• n_t – index of refraction of transmitted medium

Returns:

cosine of the critical angle