If the size of the scattering particles is extremely fine, which color of light do they scatter?

The figure below shows the refraction of a ray through a prism. Copy the diagram and,ignoring dispersion at the faces $AB$ and $AC$,mark the following angles: $(i)$ The angle of incidence,$(ii)$ the angle of refraction at the face $AB$,$(iii)$ the angle of emergence,and $(iv)$ the angle of deviation.

$A$ $14$ 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.

List four common defects of vision that can be corrected with the use of spectacles.

In the case of the human eye,when light rays enter the eye,most of the refraction occurs at the

The focal length of the eye lens can be changed due to the action of $......................$.