$A$ person has a near point at $60\; cm$. The focal length of the spectacle lenses required to read at $22\; cm$,with the glasses separated by $2\; cm$ from the eyes,is: (in $; cm$)

For a normal eye,the least distance of distinct vision is......$m$.

$A$ student can distinctly see objects up to a distance of $15 \, cm$. He wants to see the blackboard at a distance of $3 \, m$. The focal length and power of the lens used,respectively,will be:

The circular part in the centre of the retina is called:

$A$ 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 $2\, cm$.)

$A$ presbyopic patient has a near point of $30 \ cm$ and a far point of $40 \ cm$. The dioptric power of the corrective lens required for seeing distant objects is: (in $D$)