Which color of light undergoes the least scattering due to the atmosphere?

$A$ person is able to see objects clearly only when these are lying at distances between $50 \text{ cm}$ and $300 \text{ cm}$ from his eye. Identify the kind of defects of vision he is suffering from. Give reason for your answer.

What is the far point of a person with normal vision?

$A$ person cannot see distinctly objects kept beyond $2\, m$. This defect can be corrected by using a lens of power ........ $D$.

Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

$A$ $14$ year old student is not able to see clearly the questions written on the blackboard placed at a distance of $5\, m$ from him.
$(a)$ Name the defect of vision he is suffering from.
$(b)$ With the help of labelled ray diagrams show how this defect can be corrected.
$(c)$ Name the type of lens used to correct this defect.