What is the far point of a normal human eye?

$(i)$ 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.

$A$ person can see distant sign boards clearly but cannot read clearly a book which is at $25\, cm$ from his eye. Giving reason,identify the defect. Draw a labelled ray diagram to illustrate this defect and its correction.

$(a)$ Explain the phenomenon of scattering of light. State the factor on which the colour of scattered light depends.
$(b)$ List any two natural phenomena based on the scattering of light.

Name the part responsible for the power of accommodation of the eye.

What is the phenomenon of splitting of white light into its seven constituent colors called?