What is the muscular structure located behind the cornea in our eye called?

$(i)$ What is the least distance of distinct vision for a normal eye?
$(ii)$ Does the above distance increase or decrease for a long-sighted eye (hypermetropia)? Give a reason for your answer with a diagram.

List four common defects of vision that can be corrected with the use of spectacles.

The colour of light which is deviated the least by a prism in the spectrum of white light is

Which lens is used to correct the defect of myopia (nearsightedness)?

How are we able to see nearby and also the distant objects clearly?