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

$A$ person with defective vision is unable to see objects nearer than $1.5 \ m$. He wants to read books at a distance of $30 \ cm$. Find the nature, focal length, and power of the lens he needs in his spectacles.

$A$ 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.

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.

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

In myopia,what happens to the power of the eye lens?