Question

A convex refracting spherical glass surface has a radius of curvature $20cm$ and refractive index of $1.5$ . A ray of light coming from a source located at $100cm$ from the glass surface strikes it. The position of the image will be formed at:

• A. $25 \, cm$ , on opposite side of source
• B. $50 \, cm$ , on same side of source
• C. $100 \, cm$ , on opposite side of source
• D. $200 \, cm$ , on same side of source

Answer 1

Answer: (C)

Here, $\mu _{1}=1, \, R=20 \, cm, \, u=-100 \, cm, \, \mu _{2}=1.5$
$\therefore \, \frac{1}{100}+\frac{1.5}{v}=\frac{1.5 - 1}{20}=\frac{1}{4}$
or $\frac{3}{2 v}=\frac{1}{40}-\frac{1}{100}=\frac{5 - 2}{200}=\frac{3}{200}\Rightarrow v=100 \, cm$
Hence, the image is formed at a distance of $100cm$ from the glass surface.