$A$ convex lens can be used to correct long-sightedness (hypermetropia).

The twinkling of stars is due to atmospheric:

$A$ person cannot read a book at distances less than $50\, cm$. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagrams to show the image formation
$(i)$ by defective eye and
$(ii)$ after using corrective lens.

Which color appears at the top of a rainbow observed in the sky?

Accommodation means the adjustment of light going into the eye for image formation.

What is meant by scattering of light? Mention the factor on which it depends. Explain why the colour of the clear sky is blue? An astronaut in space finds the sky to be dark. Explain the reason for this observation.