The far point of a myopic person is $40 \, cm$. What type of lens should they wear to see distant objects clearly? Calculate the focal length and the power of the lens they should use.

$A$ person cannot read a book at distances less than $50\, cm$. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagrams to show the image formation
$(i)$ by defective eye and
$(ii)$ after using corrective lens.

Why does it take some time to see objects in a cinema hall when we just enter the hall from bright sunlight? Explain in brief.

What is meant by accommodation of the eye?

$A$ person cannot see objects distinctly when placed at a distance less than $50\, cm$.
$(a)$ Identify the defect of vision.
$(b)$ Give two reasons for this defect.
$(c)$ Calculate the power and nature of the lens he should be using to see clearly the object placed at a distance of $25\, cm$ from his eyes.
$(d)$ Draw the ray diagrams for the defective and the corrected eye.

When one enters a dim-lit room from bright light,one is unable to see the objects in the room for some time. Explain why.