Question

A ray of light is incident on a thick slab of glass of thickness t as shown in the figure. The emergent ray is parallel to the incident ray but displaced sideways by a distance d. if the angles are small then d is

• A. $t(1-\frac{i}{r})$
• B. $rt(1-\frac{i}{r})$
• C. $it(1-\frac{r}{i})$
• D. $t(1-\frac{r}{i})$

Answer 1

The correct option is C $it(1-\frac{r}{i})$

The lateral shift occured in the ray is given by:

$d=\frac{t\sin (i-r)}{\cos r}$

For small angle, $\sin (i-r)\approx i-r$

$\cos r\approx 1$

$d=\frac{t(i-r)}{1}=it(1-\frac{r}{i})$