The eye defect known as $Presbyopia$ is corrected by using a $........$ lens.

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

How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.

The figure below shows a glass prism placed in the minimum deviation position. $A$ ray of monochromatic light is incident on its face $AB$. Copy the diagram and show the refracted and the emergent ray. Mark the angle of deviation. State any two factors on which the angle of deviation depends.

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

$(a)$ Explain the following terms used in relation to defects of vision and corrections provided for them:
$(i)$ Myopia $(ii)$ Astigmatism $(iii)$ Bifocal lenses $(iv)$ Far-sightedness (Hypermetropia).
$(b)$ Describe with a ray diagram how a person with myopia can be helped by spectacles.