Question

The eye can be regarded as a single refracting surface. The radius of curvature of this surface is equal to that of cornea $7.8\text{mm}$. This surface separates two media of refractive indices $1$ and $1.34$. Calculate the distance from the refracting surface at which a parallel beam of light will come to focus.

• A. $1\text{cm}$
• B. $2\text{cm}$
• C. $4.0\text{cm}$
• D. $3.1\text{cm}$

Answer 1

The correct option is D $3.1\text{cm}$

Using refraction at curved surfave is,

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

$R=7.8\text{mm}$


Given,
${\mu }_1=1{\mu }_2=1.34$

$\Rightarrow \frac{1.34}{v}-\frac{1}{\infty }=\frac{1.34-1}{7.8}[\because u=\infty ]$
$\therefore V=30.7\text{mm}=3.07\text{cm}\approx 3.1\text{cm}$.