A man who wears glasses of power 3D must holds a newspaper at least 25 cm away to see the print clearly. How far away would the newspaper have to be if he took off the glasses and still wanted clear vision?

Step-by-step solution

Given, power P=3 Df= 1 P = 1 3 ~m = 100 3 ~cm . u=-25 ~cm Applying lens formula, we can write 1 v - 1 u = 1 f 1 v + 1 25 = 3 100 1 v = 3 100 - 1 25 = 3-4 100 = -1 100 v=-100 ~cm Now, again using lens formula we can write 1 v - 1 u = 1 f As, focal length of a far sighted person deceases 1 -100 - 1 u 1 1.7 = 10 17 [ f 1.7 ~cm ] aligned & 1 u -1 100 - 10 17 & = -17-1000 1700 = -1017 1700 aligned u 1700 1000 -1.7=-1 ~m (nearest option)