Which part of the eye controls the amount of light entering it?

Explain the following terms connected with the eye:
$(i)$ Ciliary muscles
$(ii)$ Accommodation
$(iii)$ Blind spot.

Explain why,when the sun is overhead at noon,it appears white?

$A$ person is able to see objects clearly only when these are lying at distances between $50 \text{ cm}$ and $300 \text{ cm}$ from his eye. Identify the kind of defects of vision he is suffering from. Give reason for your answer.

Short-sightedness (myopia) is caused due to the elongation of the eyeball.

Which of the following statements is correct?