The colour of which part of the eye determines the colour of the eye of a person?

Which lens is used to correct the defect of hypermetropia (farsightedness)?

What would have been the colour of the earth's sky if there were no atmosphere?

What are the two colors of light called whose mixture produces white light?

Is the position of a star as seen by us its true position? Justify your answer.

$A$ student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct?