Make a diagrant to show how hypcnnctropia is corrected. The near point of a hypermetropia eye is l m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25cm

Make a diagrant to show how hypcnnctropia is corrected. The near point

1.	Make a diagrant to show how hypcnnctropia is corrected. The near point of a hypermetropia eye is l m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25cm
Answer» Solution :A person suflering frorn hypennetropia can see distant OBJECT clearly but faces difficulty in seeing nearby OBJECTS clearly. It happens because the eye lens focuses the incoming divergent rays beyond the retnia This defect of vision is corrected by using a CONVEX lens. A convex lens of suitable power converges the in co1n ing light in such a way that the image is formed on the RETINA, as shown in the following figure The convex lens actually creates a virtual image of a near by object (Nin the figure) at the near point of vision (N) of the person suflering from hypennetropia. The given person will be able to clearly see the object kept at 25cm (near point of the nonnal eye) if the inmge of the object is formed at his near point which is given as 1m. Object distance, u =25m Image distance, v=1m=-100m Focal length , f Using the lens FORMULA `(1)/(v)-(1)/(u)=(1)/(f)` `-(1)/(100)-(1)/(-25)-(1)/(100)` `(1)/(f)=-(1)/(25)-(1)/(100)` `(1)/(f)=(4-1)/(100)` `f=(100)/(3)=33.3=0.33m` W.K.T Power,` P=(1)/(f("inmetere"))` `p=(1)/(0.33)=+3.0D` a convex lens of power + 3.OD is requited to correct the defect