Which lens is used to correct the defect of myopia (nearsightedness)?

$A$ student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw a ray diagram for the correction of this defect.

Name the colours of the visible spectrum.

$(i)$ What is meant by dispersion of white light? Draw a diagram to show the dispersion of white light by a glass prism.
$(ii)$ Light of two colours $A$ and $B$ pass through a prism. $A$ deviates more than $B$ from its path of incidence. Which colour has a higher speed in the prism?

Which part of the eye is responsible for adjusting the size of the pupil?

What color does a red rose appear when green light is incident upon it?