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A person needs a lens of power 5.5 dioptre for correcting his distant vision. For correcting his near vision he needs a lens of power+ 1.5 dioptre. What is the focal length of the lens required for correcting (i) Distant vision and (ii) Near vision? |
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Answer» Solution :For distance vision =0.181m, for near vision=0.667m.The POWER P of a lens of FOCAL length F is given by the reaction `p=(1)/(F("inmeters"))` (i) Power of the lens used for correcting distant vision == -5 .50 Focal length of required lens`F= (1)//(p)` `F=(1)/(-5.5)=0.181m`The focal length of the lens for correcting distance vision is 0.181. (ii) Power of the lens used for correcting near vision =+ 1.5D Focus length of the required lens,`F=(1)//(P)` `F= (1)/(1.5)=+0.667m.` |
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