Question

A nearsighted person has a far point of 25.525.5cm and is prescribed contact lenses to correct her vision. What lens strength (a.k.a., lens power), in Diopters, should be prescribed

Answer 1

Answer:

The right answer is "-3.90 D".

Explanation:

According to the question,

Far point,

v = -25.525 cm

and,

u = $\infty$

By using the lens formula, we get

⇒ $\frac{1}{f} =\frac{1}{v} -\frac{1}{u}$

On putting the values, we get

⇒     $=\frac{1}{-25.525} +\frac{1}{\infty}$

⇒  $f=-25.525 \ cm$

or,

⇒     $=-25.6 \ cm$

hence,

⇒ $Power (P)=\frac{100}{f}$

⇒                  $=\frac{100}{-25.6}$    

⇒                  $=-3.90 \ D$