A light ray is incident on a flat piece of glass with index of refraction $n$ as in Fig. $32-24 .$ Show that if the incident angle $\theta$ is small, the emerging ray is displaced a distance $d=t \theta(n-1) / n,$ where $t$ is the thickness of the glass, $\theta$ is in radians, and $d$ is the perpendicular distance between the incident ray and the (dashed) line of the emerging ray (Fig. $32-24$ ).