Fill in the blanks :
_________ lens is used to correct the defect of vision formed as presbyopia.

Q. The bifocal lens used in the correction of presbyopia has a lens on upper side and a lens on lower side.

Q. A person is advised to use a lens of power +2 D for correcting his vision. Identify the defect of vision, and find the focal length of the lens.

Q. To read a poster on a wall, a person with defective vision needs to stand at a distance of $0.4m$ from the poster. A person with normal vision can read the poster from a distance of $2.0m$. Which one of the following lens may be used to correct the defective vision?

Q. In presbyopia,the near point of the eye gradually recedes away. Thus it is a case similar to hypermetropia. The why shouldn't we use a convex lens to correct this defect instead of a bifocal lens?

Q. The defect of vision which cannot be corrected by using spectacles is :
(a) myopia (b) presbyopia (c) cataract (d) hypermetropia