Pigments are mixed by the $......$ method to produce various colors.

$A$ 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.

Which two colors of light combine to form the color maroon?

$A$ 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.

Draw ray diagrams each showing $(i)$ myopic eye and $(ii)$ hypermetropic eye.

What would have been the colour of the earth's sky if there were no atmosphere?