Question

For a normal eye, The cornea of eye provides a converging power of $40D$ and the least converging power of the eye lens behind the cornea is $20D$. Using this information, the distance between the retina and the cornea eye lens can be estimated to be.

• A. $1.5cm$
• B. $5cm$
• C. $2.5cm$
• D. $1.67cm$

Answer 1

The correct option is D $1.67cm$

Power of Cornea, $P_1=40D$
and power of the eye lens, $P_2=20D$

$P_{eff}=P_1+P2$
$\Rightarrow P_{eff}=40D+20D=60D$

So, $f=\frac{100}{P_{eff}}=\frac{100}{60}=1.67cm$
Hence, the correct option is $\left(D\right)$