The diameter of the eye-ball of a normal eye is about $2.5\, cm$. The power of the eye lens varies from

$A$ person has a near point of $50\, cm$. What lens should they use to reduce it to $25\, cm$?

Assertion : In a movie, ordinarily $24$ frames are projected per second from one end to the other of the complete film.
Reason : The image formed on the retina of the eye is sustained up to $1/10 \, s$ after the removal of the stimulus.

$A$ myopic adult has a far point at $0.1\, m$. His power of accommodation is $4\, D$.
$(i)$ What power lenses are required to see distant objects?
$(ii)$ What is his near point without glasses?
$(iii)$ What is his near point with glasses? (Take the image distance from the lens of the eye to the retina to be $2\, cm$.)

The near point of a hypermetropic person is $75\, cm$ from the eye. What is the power of the lens required to enable the person to read clearly a book held at $25\, cm$ from the eye?

Match the List-$I$ with the List-$II$ from the combinations shown:

$(I)$ Presbyopia	$(A)$ Sphero-cylindrical lens
$(II)$ Hypermetropia	$(B)$ Convex lens of proper power may be used close to the eye
$(III)$ Astigmatism	$(C)$ Concave lens of suitable focal length
$(IV)$ Myopia	$(D)$ Bifocal lens of suitable focal length