Question

The picture given here shows a person wearing 'half-moon' spectacles. What sort of eye-defect do you think he has ? Why are these particular spectacles useful to him ?

Answer 1

Half moon spectacles are used for reading. so, the person has long-sightedness.
These particular spectacles are useful to him since the convex lenses of spectacles form the image of nearby object (like a book in hand) at the near point of his eye.