Question

The image for the converging beam after refraction through the curved surface is formed at

• A. $40cm$
• B. $\frac{40}{3}cm$
• C. $20cm$
• D. $\frac{180}{7}cm$

Answer 1

The correct option is A $40cm$

It is clear that the object is virtual and the image is real.

$\frac{n_i}{v}-\frac{n_o}{u}=\frac{n_i-n_0}{R}\frac{1}{v}-\frac{\frac{3}{2}}{(+30)}=\frac{1-\frac{3}{2}}{+20}\frac{1}{v}=\frac{1}{20}-\frac{1}{40}\Rightarrow v=40cm$