Question

The eye can be regarded as a single refracting surface. The radius of curvature of this surface is equal to that of the cornea $(7.8mm)$ . 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. $4.0cm$
• B. $1cm$
• C. $2cm$
• D. $3.07cm$

Answer 1

Answer: (D)

We know eye lens is convex refracting surface.
Use expression for refraction from curved surface

${\mu }_1\to$ Refractive index of medium having incident ray
${\mu }_2\to$ Refractive index of a medium having reflected ray
$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$
$\frac{1.34}{v}-\frac{1}{\infty }=\frac{1.34-1}{7.8}$
$v=30.7mm$
$v=3.07cm$