Which of the following phenomena of light are involved in the formation of a rainbow?

On what factor does the colour of the scattered light depend?

State one function each of iris,pupil,and cornea.

In which direction is a rainbow formed during the morning hours in the rainy season?

What is the time difference between the actual sunset and the apparent sunset?

$A$ student finds the writing on the blackboard blurred and unclear while sitting on the last desk in a classroom. He,however,sees it clearly while sitting on the front desk at about $2\, m$ from the blackboard.
$(a)$ Draw ray diagrams to illustrate the formation of image of the blackboard writing by his eye lens when he is seated at the $(i)$ last desk,$(ii)$ front desk.
$(b)$ Name the defect of the eye from which the student is suffering.
$(c)$ Name the kind of lens that would help him to see clearly even when he is seated at the last desk. Draw a ray diagram to illustrate how this lens helps him to see clearly.