Question 198 of 295

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$3.07 cm$

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Answer: (D) $3.07 cm$

We know eye lens is convex refracting surface.

Use expression for refraction from curved surface



${\mu }_{1}\rightarrow$ Refractive index of medium having incident ray

${\mu }_{2}\rightarrow$ Refractive index of a medium having reflected ray

$\dfrac{{\mu }_{2}}{v}-\dfrac{{\mu }_{1}}{u}=\dfrac{{\mu }_{2}-{\mu }_{1}}{R}$

$\dfrac{1.34}{v}-\dfrac{1}{\infty }=\dfrac{1.34-1}{7.8}$

$v=30.7 mm$

$v=3.07 cm$