Which optical phenomenon is responsible for the formation of a rainbow?

$(a)$ State the reasons which lead to hypermetropia. With the help of suitable diagrams,explain this defect of vision and its correction.
$(b)$ Draw a diagram of an experimental arrangement for observing the scattering of light in a colloidal solution. Name the two chemicals used in this activity.

$A$ bifocal lens consists of both concave and convex lenses. Bifocal lenses are required by a person suffering from $.............$.
$P$ - Myopia (nearsightedness)
$Q$ - Hypermetropia (farsightedness)
$R$ - Presbyopia

Draw a ray diagram showing the refraction of light through a glass prism and mark the following:
$(a)$ Incident ray
$(b)$ Emergent ray
$(c)$ Refracted ray
$(d)$ Angle of incidence
$(e)$ Angle of deviation
$(f)$ Angle of emergence

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.

Why do we observe the seven colours when white light passes through a glass prism? Which component of white light deviates the least?