Name the defects of vision of the human eye.

At noon,the sun appears white because:

What is the other name of long-sightedness?

Which part of the eye helps in changing the focal length of the eye lens to focus the image of objects lying at varying distances from the eye?

$A$ narrow beam $PQ$ of white light is passing through a glass prism $ABC$ as shown in the diagram.
Trace it on your answer sheet and show the path of the emergent beam as observed on the screen $DE$.
$(i)$ Write the name and cause of the phenomenon observed.
$(ii)$ Where else in nature is this phenomenon observed?
$(iii)$ Based on this observation,state the conclusion which can be drawn about the constituents of white light.

Why do we have two eyes for vision instead of just one?