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

$A$ 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 $; cm$)

$A$ far-sighted man who has lost his spectacles reads a book by looking through a small hole $(3-4 \,mm)$ in a sheet of paper. The reason is:

$A$ person wears glasses of power $-2.5 \, D$. The defect of the eye and the far point of the person without the glasses are respectively

In the human eye,the focusing is done by:

The substance present in the choroid is: