Question

Find 'x'; such that, the ray becomes parallel to principal axis after refraction through spherical surface.

• A. 180 cm
• B. 120 cm
• C. 60 cm
• D. 30 cm

Answer 1

The correct option is A 180 cm

Apply formula for refraction through curved surface
$\frac{n_2}{v}-\frac{n_1}{u}=\frac{n_2-n_1}{R}$
$\frac{2}{\infty }-\frac{1.5}{(-x)}=\frac{2-1.5}{+60}=\frac{1}{120}$
$\frac{1.5}{x}=\frac{1}{120}$
$x=180\text{cm}$