Where is the image formed in an eye suffering from near-sightedness?

Sushil went to an eye specialist for a check-up. The doctor prescribed him to use spectacle lenses of $+0.5 \text{ D}$ power.
$(a)$ Name the defect of vision he is suffering from.
$(b)$ Find the focal length of the spectacle lens.

What is meant by scattering of light? Use this phenomenon to explain why the clear sky appears blue or the sun appears reddish at sunrise.

Give one cause of long-sightedness (hypermetropia).

Why does the clear sky appear blue? How would the sky appear in the absence of Earth's atmosphere?

$A$ child sitting in a classroom is not able to read clearly the writing on the blackboard.
$(a)$ Name the type of defect from which his eye is suffering.
$(b)$ With the help of a ray diagram show how this defect can be remedied.