What kind of lens is used in the spectacles of a person suffering from myopia (near-sightedness)?

When a light ray travels from an optically denser medium to an optically rarer medium, what is the angle of incidence called at which the angle of refraction becomes $90^{\circ}$?

$A$ glass slab is placed over a page on which the word $VIBGYOR$ is printed with each letter in its corresponding colour. $(i)$ Will the image of all the letters be in the same place? $(ii)$ If not, state which letter will be raised to the maximum. Give a reason for your answer.

Where is the image formed in an eye suffering from long-sightedness?

Identify the correct statement regarding the propagation of light of different colours of white light in air.

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