Prove that a ray of light incident on the surface of a sheet of plate glass of thickness $t$ emerges from the opposite face parallel to its initial direction but displaced sideways, as in Fig. 35-37. Show that, for small angles of incidence $\theta$, this displacement is given by
$$x=t \theta \frac{n-1}{n}$$
where $n$ is the index of refraction of the glass and $\theta$ is measured in radians.