(i) Dolly is suffering from myopia or short sightedness.
(ii) Two possible cause of this defect are :
Increase in size of eye ball or decrease in focal length of eye lens.
(iii) Here,`x = 50 cm`
`f =-50 cm`
`P = (100)/(f) = (100)/(-50)= -2 D`
(iv) Ritu has displayed concern for her friend. She has explained to her that there is no cause for worry and Dolly can be treated for her problem. And the doctor has provided Ritu right.