When we see an object,the image formed on the retina is

$A$ student studying the similarities and differences between a camera and the human eye makes the following observations:
$I$. Both the eye and the camera have convex lenses.
$II$. In order to focus,the eye lens expands or contracts while the camera lens moves forward or backward.
$III$. The camera lens produces upside down real images while the eye lens produces only upright real images.
$IV$. $A$ screen in a camera is equivalent to the retina in the eyes.
$V$. $A$ camera adjusts the amount of light entering in it by adjusting the aperture of the lens. In the eye,the cornea controls the amount of light. Which of the above statements are correct?

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

$A$ person who can see things most clearly at a distance of $10 \, cm$ requires spectacles to enable him to see clearly things at a distance of $30 \, cm$. What should be the focal length of the spectacles?

The far point of a myopic eye is at $40 \, cm$. To correct this defect,the power of the lens required will be: (in $, D$)

$A$ man can see objects clearly between $15 \ cm$ and $30 \ cm$. He uses a lens to see far objects. Due to the lens used,the new near point will be at........$cm$.