After passing through the pupil, light rays fall on which part of the eye and undergo refraction?

What color of light is produced when blue and yellow light are superimposed?

$A$ 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.

Why does the clear sky appear blue? How would the sky appear in the absence of Earth's atmosphere?

With the help of scattering of light,explain the reason for the difference in colours of the Sun as it appears during sunrise/sunset and noon.

The human eye forms the image of an object at its