A person uses +1.5 D glasses to have normal vision from 25 ~cm onwards. He uses a +20 D lens as a simple microscope to see an object. What is the maximum magnifying power if he uses the microscope without glasses.

Step-by-step solution

Let d be the distance of near point of the person without glasses. Focal length of glasses, f₁= 100 P₁ = 100 1.5 = 200 3 ~cm Now u=-25 ~cm ; v= ? From lens formula, 1 v - 1 u = 1 f₁ or 1 v = 1 f₁ + 1 u = 3 200 - 1 25 =- 5 200 v=- 200 5 =-40 ~cm Therefore, the near point of the person is 40 ~cm . Focal length of microscope, gathered f₂= 100 P₂ = 100 20 =5 ~cm M=1+ | d f₂ |=1+ 40 5 =9 gathered