Question

The image of the converging beam after refraction through the curved surface (in the given figure) is formed at :

• A. $x=40$cm
• B. $x=\frac{40}{3}$cm
• C. $x=-\frac{40}{3}$cm
• D. $x=\frac{180}{7}$cm

Answer 1

The correct option is A $x=40$cm

Option A is correct

$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{\mu }=\frac{{\mu }_2-{\mu }_1}{R}$

$\therefore \frac{1}{v}-\frac{3/2}{30}=\frac{1-3/2}{20}$

$\frac{1}{v}-\frac{1}{20}=\frac{1}{40}$

$\frac{1}{v}=\frac{1}{20}-\frac{1}{40}$

$=\frac{2-1}{40}$

$=\frac{1}{40}$

$v=40cm$