What happens to the lens and the ciliary muscles when you are looking at distant objects?

Why can you not see an object clearly if it is placed very close to your eye?

$A$ prism causes dispersion of white light while a rectangular glass block does not. Explain.

$(a)$ State the reasons which lead to hypermetropia. With the help of suitable diagrams,explain this defect of vision and its correction.
$(b)$ Draw a diagram of an experimental arrangement for observing the scattering of light in a colloidal solution. Name the two chemicals used in this activity.

Draw ray diagrams each showing $(i)$ myopic eye and $(ii)$ hypermetropic eye.

Which of the following is true for the eye defect known as hypermetropia (farsightedness)?