Reflectance and Transmission
-
When light is incident on a transparent material,
the beam is partially reflected and partially transmitted.
The transmitted and reflected intensities of parallel (||) and perpendicular (\(\perp\))
polarization light are given by Fresnel's equations –
$$R_{\parallel} = \frac{n_{t}\cos \Theta_{i} - n_{i}\cos \Theta_{t}}
{n_{t}\cos \Theta_{i} + n_{i}\cos \Theta_{t}}$$
$$R_{\perp} = \frac{n_{i}\cos \Theta_{i} - n_{t}\cos \Theta_{t}}
{n_{i}\cos \Theta_{i} +n_{t}\cos \Theta_{t}}$$
$$T_{\parallel} = \frac{2n_{i}\cos \Theta_{i}}
{n_{t}\cos \Theta_{i} + n_{i}\cos \Theta_{t}}$$
$$T_{\perp} = \frac{2n_{i}\cos \Theta_{i}}
{n_{i}\cos \Theta_{i} +n_{t}\cos \Theta_{t}}$$
Where R stands for reflection and T for transmission and \(\Theta_{i}\) is angle of
incidence and \(Theta_{i}\) is the angle of refraction.
-
At a particular angle of incidence, the reflected and transmitted rays are perpendicular
to each other and also reflected light is polarized. This incident angle is given by
$$\Theta_{i} = \tan^{-1} \left( \frac{n_{t}}{n_{i}} \right)$$
This particular angle is referred to as Brewster’s angle.