Question

a beam of light is converging towards a point $I$. A plane parallel plate of glass of thickness t, refractive index $\mu$ is introduced in the path of the beam. The convergent point is shifted by (assume near normal incidence) :

• A. $t(1-\frac{1}{\mu })away$
• B. $t(1+\frac{1}{\mu })away$
• C. $t(1-\frac{1}{\mu })nearer$
• D. $t(1+\frac{1}{\mu })nearer$

Answer 1

The correct option is A $t(1-\frac{1}{\mu })away$

$\mu =\frac{D}{d}$

Where $D=$real depth and $d=$apparent depth.

$\therefore d=\frac{D}{\mu }=\frac{t}{\mu }$

Also, shift $S=D-d=t-\frac{t}{\mu }=t\left(1-\frac{1}{\mu }\right)$

From the picture we can see that the shift is away from the converging point.

Hence the correct answer is option (A) $t\left(1-\frac{1}{\mu }\right)$ away.