The human eye forms the image of an object at its

What is the eye lens made of?

Which color of light has the minimum velocity in a prism?

$(a)$ State two main causes of a person developing near-sightedness (myopia). With the help of a ray diagram, suggest how this disability can be corrected.
$(b)$ The far point of a myopic person is $150 \ cm$ in front of the eye. Calculate the focal length and power of the lens required to enable him to see distant objects clearly.

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

$A$ near-sighted person can see only nearer objects.