Answer to Question #214890 in Optics for lala

Question

Ahmad has a far point of a mere 50 cm. He uses a contact lens to see the distant object clearly. What is/are the condition(s) about the contact lens?

A. The contact lens is a concave lens.

B. The contact lens is a diverging lens.

C. The focal length of the contact lens is -50 cm.

D. The power of the contact lens is -2.0 D

Answer 1

Answer

Its Near sightedness because he can not see beyond 50cm.

So he has to use concave lens. Which is also known as diverging lens.

By lenses formula

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

V=-50cm

And $u=\infin$

So

$f=-50cm$

And

Power

$P=\frac{1}{f}=\frac{1}{-50}=-2.0D$

So A, B, C and D all are correct.